I have a 1990 K3500 Silverado with a throttle body injected 454 engine and 400 Turbo 3 speed automatic transmission. The problem I am having is the engine bogs down ever so slightly when you take off, or get into the throttle a bit at highway speed. It doesn't seem to do it till in 2nd & 3rd gear when taking off, unless I just don't notice it because of the big motor and 3:73 gears. I had read on another website that specializes in GM throttle body fuel injecton that the O2 sensor could be the problem. They claim that a modified free flowing exhaust system will not heat the single wire, non heated O2 sensor (which my truck had,) enough to monitor the exhaust properly. My truck still has the 2 into 1 exhaust setup, but has had the catalytic converter removed and also has a Flowmaster muffler on it. And another thing the site said was that removing the cat was one of the biggest causes of this problem. They had also said that the cure for this problem was to go from a single wire (non heated) O2 sensor, to a 3 or even 4 wire heated O2 sensor because they monitor a lot better. I went out this morning and installed a 4 wire O2 sensor on it, drove it down the road, and only difference I could feel from doing this was the truck didn't bog down under throttle at highway speed anymore. The engine has been slightly modified with an Edelbrock Performer Plus cam, Performer T.B.I. intake, new Venom fuel injectors, and an adjustable fuel pressure regulator. But I had this problem before I ever made any mods to the truck. If anyone could give me some kind of clue as to what's causing this, that would make my day. I should also note before someone suggest it, I've already put a new fuel pump and filter on it as I know that this can cause the same trouble.