my stock 12/10 had a 43 jet in it and that was factory safe (rich-ish). if he's all stock a 49 is too big. but yah, clean up your air box, I took all the internals out so it flows better did that with the 43 jet stock pipe it was better. got the good Polini Pipe and jumped to a 50 a 49 might be better. Tried a 52 with just pantyhose fouled the plug. tried a high flow air filter (treats) with the fifty back in didn't sound happy. so i put the stock gutted box back on. happy as could be. I'll hold off on the high flow and up jet till I get the 13.13 which as I understand comes with a 66 jet. check out the tuners spread sheet, it is so useful. there is a link in the wiki or can just search "spread sheet" in Performance and it will come up. remember altitude and temp make a big difference when you're looking at other peoples setups. I'm in San Francisco (sea level) and its pretty cold so I doubt you'll need bigger jets than me. but hey size doesn't matter. Oh wait it does doesn't it.