2.8 on my LQ4 made 8#. With ported heads and comp 54-444-11 cam, GT2-3 cam, longtubes and ported and polished 317's. MP122 with 2.8, A&A cam other mods the same makes 10.5#.

 

Hell, I don't remember If I have 2.9 or 2.8 pulley on it. Anyway. About 55K miles on two different engines @ 8 - 11 psi. (Load temp dependent). I always spray meth above 2 psi. A bad cam took out the first engine. So not boost related. I'm not overly hard on it on the street but do occasionally thrash it. Dozens if not over a hundred full tilt passes down the 1/4. Dozens of passes with nitrous both on and off the track.

 

A 2.75" pulley gave my right at 8psi on my LQ9. Thats with good exhaust and the normal supporting mods.

 

I had a 3.0 ply on my 112 and I got 9ish out of it, thats on a 5.3 also.

 

I get an average of about 8.5 psi 2.9 pulley on an LQ4.... Boost will drop off in the upper rpm's as the radix runs out of breath.