Ideas for a 00 S281 Saleen mods

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My buddy just got a 2000 S281 Saleen with about 20k miles, car runs great, but just didn't seem to pull up top quite as hard as it should, so we dynoed it.
We got 273 SAE rwhp and the torque number seemed real good, don't remember exactly but ~340 seems like what I recall. Dyno room was about 75 deg, not bad with pretty low humidity. On a nice cool day I'm sure even the corrected numbers would be better. It also has the optional rims and 295 tires on the back, don't know how much that will effect the numbers. Boost go's to about 5 and then slowly climbs to 7 or so by 5800 rpm. If every thing seems about right what would be some good bang for the buck mods? Would an x-pipe and smaller pulley wake it up a bit more? Any suggestions would be greatly appreciated.