Two quick questions about the throttle body.

First (most important), what size is the stud on the front that holds the bracketry? It's the stud highlighted in this picture (thanks to blazerforum member myDownfall for the pic I borrowed for this):



Mine was replaced by someone with a sheet metal screw, then broken off and left to rust with the brackets just laying there.

My throttle body is in the drill press now, and I've drilled it out mostly. It looks like the stud might be the same size as the upper plenum studs. Maybe 1/4-20. I need to know which heli-coil to stick in it and what size stud actually belongs there.

Second question, what about removing the throttle blade obstruction (diffuser?) while I have it off? I'm doing some searches here and elsewhere now about this. It looks like it's obstructive at wide throttle openings, but might actually help smooth the flow at part throttle. I'd rather not compromise part throttle (mid range) fuel economy. If it helps that, I'll leave it. Also, if it helps mid range efficiency, I might even experiment with a solid version on the opposite side of the blade.

 

Taking a quick break and answering part of my own question here.

The studs for the upper plenum are M6x1.0, not 1/4-20, and I have M6x1.0 heli-coils (taps, drill bits, etc.) and some bolts and some studs in that size, so that's what it's getting. I don't care if it's "stock" or not, it will work.

Still a little curious about the mod to the deflector/diffuser/obstruction, but I can do that later if I want to experiment.

 

I removed my diffuser and it has a noticeable difference from zero throttle off the line but after that I notice no difference. As far as mpg I have no idea I have 40" tires so I measure my fuel in gpm!