Try some GM syncromesh. Good stuff. I've got an MR2 as well and just put it in, and it seems to have cured my 3rd gear crunch. Only problem with the Redline and GM fluid is that they're not GL-5 (something like that) they're one step lower. There's some controversy over at the MR2 boards as to whether they will do long term damage to the trannies. Something about the sulfer eating the plastic in the tranny. If I were you and had money, I'd go with a 93+ tranny, as it has the limited slip differential and better syncros that won't crap out on you as easily. You can buy them new from Toyota for $1640 or find someone selling them used.

Todd