As noted by the previous poster. The cars weight is heavier than their electric brotheren counterparts, but not adnormally heavy for its platform....which is street bashing/racing and mild club(read, local hobby shop) racing. With that said, there are still plenty of hop-up parts you can get to lighten the car up and increase performance. However, when doing so, you reduce the duriblity of the car (basiclly it can't take the same punishment as before).
1) Get a lighter screw set. This means usually means going from the stock stainless steel screws to the titainium screws or aluminum screws. Many screw kits can be found online at hobby shops or ebay or do search for screw kits for HPI RS4 3 Evo. Heck HPI even has their own online shop:
For a little more than half the price of your car you can lighten up your chassis consideribly
#73914 SUPER CHASSIS (3mm 7075/NITRO 3) http://www.hpiracing.com/products/en/73914/
#73056 UPPER DECK (WOVEN GRAPHITE/NITRO 3)
#73047 FRONT SHOCK TOWER (GRAPHITE/NITRO 3)
#73048 REAR SHOCK TOWER (GRAPHITE/NITRO 3)
Find other hop-ups availabe here:
Now, with all the hop-ups added you car is now lghter, faster, and turns sharper, however; this is also a double-edge sword. Any mistake you make, while driving will will seem 2 or 3 time more critical and as I said before your car is more fragil so take care and practice, practice, practice!