I have a chev 1/2 ton with a 350 tbi. The engine pulls realy good to about 4000 and then it makes this lame fluttering sound and lays down but as soon as it shifts it picks up hard again. This only occurs at full throttle if I back off just a bit its good to 4500 or so. The ignition is in good condition and the engine is stock other than high flow exhaust, air intake, msd, pullies, hypertech 160 thermo. I have the fuel pressure at 13 psi. If the fuel pressure was the problem wouldnt it show at all engine speeds at wot ? Or any other suggestions would be great.

 

I think your first problem is the 160 t-stat. I had to change mine to a 180 and it helped a whole lot. Your gauge probably doesn't move much past the 100 degree mark huh? The biggest problem that I have noticed with the TBI motors is the stock cam and intake manifold don't allow much power after 4500 rpms. I have a Comp Cam 268h and I still have the same problem at high rpm. Guess I need an Edelbrock intake. I am not sure about the fluttering.

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'87 Silverado
350 4 bolt main bore .040 over
TB Injected
Ported and Polished heads
Comp cams 268h cam and top end
Flowtech headers
3.73s on Detroit locker