RJC power plate makes more HP, cures most of the fuel distribution issues, reduces knock due to the better distribution of the air, and is cheaper! Stock upper is poop too. Port the manifold, and remove the egr bosses! At LEAST remove the egr boss from the upper. You can probably add a couple hundred bucks for manifold work, and gain MUCH, MUCH more HP. Ask the guys in the 9s with stock t bodies!
Just my opinion.
It seems the stock plenum is only slightly larger than the stock throttle body and the plenum inlet is not always lined up. Steve Monroe opens up the plenum inlet for his 62mm mod, or he did when he was still doing them.
Just gasket match the plenum inlet.
The Precision plenum w/ power plate has a little better air distribution than the stock plenum w/ power plate.
The Precision plenum is 5/8” taller than stock for clearance around a 4” maf pipe, just a heads up.
An Accufab plenum is the same height as stock.
I had a machine shop taper my precision plenum so the throttle body lined up better with the up pipe and to clear the hood pad.