$2900 is enough for a motor swap and some mods to the turbo motor. I highly suggest he spend no money souping up the n/a engine and just go for broke on the turbo engine. There are some mods out there for the non-turbo engine but the non-turbo engine is basically built for economy and tourque. $2900 is plenty to swap in a turbo engine it would be the easiest way to drop 1 and half seconds off his 1/4 and actually have a car that looks fast be fast. A body kit and stuff will only make the car slower. If he needs help finding a good turbo engine just let me know I am pretty well knee deep in the MR2 scene to find him something nice.

If he still wants to do stuff to the non-turbo engine then he really only has a few things he can do intake headers eshaust and nitrous. Intake headers and exhaust will run him about a grand. Then after these mods the clutch will give out so then a performance clutch and labor runs about another $600. and then a nitrous kit next for $500 but you then are still slower than a stock turbo car would be.

I bought my motor and payed for the labor for a swap and it cost me a little less than $4000 but my motor was already modified. He could prolly find a full swap for just under $2000 do the labor himself and then have left over money for a park bench spoiler or something.