Over the years, I have run many different MAF pipe vs compressor cover combinations. Everything from a stock turbo with 3" maf pipe, to my current PT6776RHP with 4" all the way and a stock MAF. Here is the break down. My grey '86 had a stock turbo, then a TE63-1 with Garrett 3" inlet, 2.5" discharge old school cover, then a LT70-1 with 4" inlet 3" discharge, then a PT74 Q-trim with old style H cover and the last upgrade was to build it to GT-Q specs but with same old style H cover 4" inlet, 3" discharge. My white Limited had a TE-45 with TO4E cover 3" inlet, 2" discharge. My current '87 T came with a TA-49, then a TE-60R, then a PT6776S and finally, PT6776RHP. Eight different MAF pipes and I always ran a stock MAF sensor, except for when I was running a FAST system on my old Grey car.
On my old White Limited, I was running a TE-45 with the E compressor cover. (3" inlet, 2" discharge) I ran a 3" MAF pipe for a little bit, until I bit the bullet and bought a chrome 4" MAF pipe from Modern Muscle car and ran the stock MAF. Even with the reducer hoses at the turbo and at the MAF, it helps with spool up and made more power. At the time, not very many people were running 4" maf pipes with stock MAF sensors. That was the setup that I had on that car when it ran an 11.07 @ 120 on 28psi. That car was very simple. It had a stock 75K mile bottom end, ported and polished M&A Stage III aluminum heads with matching intake, Hemco upper plenum, modified stock 62mm t-body, Direct Scan, Scanmaster, fuel system, FM IC, Art Carr 16930 9" non l/u converter, typical suspension parts, 3" exhaust all the way back and C-16 back in '98.
Fast forwarding now.
Recently, while running the 6776S turbo, I had to run the 3" MAF pipe and stock MAF with just a K&N cone attached to it. I could tell just by listening and feel, that the turbo was struggling because of having to suck through such a small setup. So I upgraded to Marks' (Buickgn) 4" MAF pipe and 4" Big Mouth cold air kit. The turbo was allowed to breath a lot easier and the car ran a whole lot smoother and quicker. Just this yesterday, I installed my new turbo and IC and let me tell you, this car is a monster now.
I would recommend to all who are running a turbo that has a 4" inlet, to upgrade their MAF pipe to at least a 3.5" if not a 4" setup, as you will see a gain in spool up and throttle response.
More to come.
Patrick