I'm swapping in a TPI 350 in my 89 Camaro 305 TBI. The 350 will make over 300 HP and about 400 ft lbs of Torque. I haven't cranked it yet, but have been reading about throttle bodies. Should I stay with the stock 48mm. or go larger. Would jumping from 48mm to 58mm be too much?? Is the difference even worth the 300 bucks?

stock one will work just fine. (not worth the $300 to me)

Most of what i have seen says to wait till >400hp

Agreed, at that point, there are worse restrictions than the throttle body that should be addressed first.

Yea, I agree. There are many articles, explaining this. I've heard that the stock Throttle body is good up to about 500+ hp. If anything I would just port it maybe alittle along with the manifold, plenum, and runners. You'd be supprised of the great effects of porting, its free too !!! You will also gain a few usable rpm's up top.

qft, porting will help out some.

Excuse my lack of knowledge but what does qft stand for ??

"Quoted for Truth"

LOL I see, cool. I see alot of new acronyms on here. Yea porting is an excellent source of power in stock intakes. I just started the giant task of gasket match porting my heads, pain in the *** but deffinately rewarding.

Awesome, thanks for the info guys- I have polished the throttle body inside. You sware it was dipped in chrome! I have ported and polished the stock intake manifold. All 8 ports are smooth as a babie's butt. Heads are Aftermarket and have been polished also, and slightly ported. I have knocked down the EGR wall in the plenum, and was looking for other ideas. Thanks again-

do a search on porting the plenum, you will find good posts & pics