good advice so far. Also, glue your tires to the wheels, especially if you're using soft tires. It helps immensely! You can use rubber cement or tacky glue, or even a light amount of super glue if you want. This removes the "wheel/tire" slip, where the tire plants to the pavement but the drive wheels still lose traction against the tire's inner surface. It doesn't take much glue to fix it, rubber cement is also easy to remove when you want to change tires off. I personally just went and bought the wheel upgrade kit and a few tire upgrade kits (for spares!) and started gluing. I just change out whole wheel/tire sets instead of digging around for 4 matching tires, and since they're already glued, it really speeds up the process of changing tires out and gluing them in the paddocks before the race.

Also, I modified the damper mounting points so that I can swap springs out without unscrewing the dampers from the control arms.

As far as setup goes, the RSX weighs less than the other cars as well. Not by much, but it does weigh less. If you are participating in an "Official" XMODS drag race and you're forced to stay within the limits of stock and XMODS official parts, the RSX may well be the winner. Longer wheelbases definitely handle better, but wheelbase has NO effect on launch, traction, or top speed.

Tire choice will depend on the surface. For unfinished smooth concrete or smooth asphalt (like a skate park or tennis court) soft slick will work fine. For finished concrete or laquered hard wood (like a basement or basketball court) you will probably want to use soft tread, but when in doubt, try all your options.

Tie rod: Stock (as mentioned before, the wheels pointing straight forward will provide less rolling resistance)

Weight: I trimmed the whole air dam off the front of my skyline. I'll post a pic of it. Bodykit is a no-go. Spoiler and mirrors removed when racing. I trimmed the plastic out from under the hood, used a dremel with a drum sander to grind away inside the body. I removed the light kit too. Weigh all stock parts against the bodykit replacements and you'll see that you'll save somewhere near a dozen grams by staying with the stock parts. Grind away some stuff and you'll save more. See note about AWD below.

Drivetrain:
* ALWAYS use the LSD Ball diff in the back.
As mentioned before:
* Long Drag Races (40' or more, let's say): RWD and tallest gearing possible for a long race. AWD adds drivetrain friction AND weight, which will hurt your top speed, and your launch with taller gearing (less torque).
* Short Drag Races: AWD And possibly shorter geearing (more traction and torque). If you can get ahold of another LSD Ball Diff, put it in the front, too. Your steering will suffer severely, but how many corners are you taking on a drag strip? You'll still be able to steer enough to stay on course if you start to veer to one side.
* As mentioned above, ball bearings are of paramount importance, but keeping them cleaned out with a pair of tweezers and properly lubricated is just as important.
* Use a light coat of graphite on the motor pinion, Y gears, and diffs.
* I polished my driveshaft with mag wheel polish. it's smooth as glass and works well with the ball bearings.


Suspension: In general, the harder the better. You don't want it to be rock stiff though, it needs a little bit of "give" to keep the wheels on the ground in case it hits small bumps. If it's too stiff, one small bump might cause the whole car to hop, causing 2, 3, or all 4 wheels to lose contact with the ground, instead of just the one that hit the bump. Doubling up springs on the dampers works pretty well.

Motors: New motors that have been broken in properly (water break-in) are a must. Even a well-broken in motor that's seen a lot of use (and abuse) will be slower than a fresh one. Setting aside a few motors strictly for competition events is probably a good idea. If you have an S211T (Drag) motor that you only use when competing in timed drags, you will probably have a motor that will last several seasons with regular use. Use "play" motors when tuning your car for the course you're going to be running. Try your hardest to NEVER use reverse in your comp motors once they're broken in. Don't let your competition motors touch or even sit within an inch of another motor or magnet Don't drop the motors, either. This can damage or weaken the magnets over time.

That said, my long drag prep is like this:
Skyline Chassis, freshly cleaned and debris removed from axles, front upper deck cover removed
Skyline body with stock parts, weight reduced by grinding away excess material, removing mirrors, command logic light kit, and spoiler
Freshly Cleaned/Lubed Bearings
Broken-In S211T (Drag) with heat sink (I could probably go without it though)
Drivetrain given fresh graphite
Double Yellow springs up front, Double Blue in rear (I only have one spring kit, 4 of each color)
LSD Ball diff in back (screws tightened snugly), RWD-only setup
Rubber-Cement Glued tires (compound varies according to surface)
Stock steering tie-rod
Fresh NiMH Cells (4x AAA)

I don't currently have (nor can I afford right now) snazzy un-sanctioned parts.

Un-Sanctioned parts:
Unless you're putting down lots of crazy torque (such as a FET-Stacked car with upgraded motor), you don't need upgraded axles. Stock ones will work fine and weigh about the same.

On an XMODS with all the "official" upgrades, Power upgrades such as higher-voltage battery setups and upgraded wiring will offer you the best bang for the buck. Followed by that, FET Stacking and motors are the next best bang for the buck. After that, weight reduction becomes viable (CF chassis and driveshafts) Options such as external power boards (the V1 upgrade for example) are only for the crazy die-hard tuners with too much battery and motor for their own good, but they will make your car crazy fast if everything else is in place.