I'll jump in here! Heck, I've even heard of people running 9's with a stock TB! But I'll bet they at least cleaned up the inherent flaws built into the factory TB and upper.
Yes, among other things I CNC bore the 57mm TB to 62mm (then taper it out to 65mm in back) but I consider the bellmouthing of the TB inlet and removal of the gross factory mismatch between the rear TB opening and the upper plenum inlet a very important part of my mods! Then, with the removal of the front half of the throttle shaft and everything gently radiused and blended in the upper plenum inlet, plus, of course, the greater flow afforded by the 5mm larger bore, there are nice gains in flow quantity AND quality to be had!
Necessary? Nah. A point I like to bring up: Did you really NEED that 2.5" or 3" exhaust system when a mandrel bent 2.25" probably would get the job done? But, you did it to flow the most you could with the combo you have, right? DITTO!
On paper, no, you don't need more flow area than the stock TB provides to go tens, but I'm the type of guy that believes in at least removing even the slightest steps or mismatches in my entire intake tract! Probably why I did my own cars' TBs when they were running 13's! I always port the inlets and outlets of turbos (stock or after market), IC inlets and outlets, bellmouth my MAF inlets, grind out the "lips" on either end of my up-pipes... you name it! It all just makes sense to me! Am I wrong?
