acceleration lag when hot

[mechtech2000]

I have a 1994 GMC suburban K1500 350 5.7 Liter. Auto trans. I had a bad load of gas 2 months ago and it started running bad. several tanks later I am stuck with a holding back sensation(like a knock sensor that is retarding timing) when the engine is hot. When the engine first runs in the morning cold it runs Flawlessly like nothing is wrong and in open loop! As it starts to warms up it begins to lack power but feels as though it wants to break through. No codes are in play and no light on! I replaced plugs, wires, cap, rotor, coil and fuel filter and air filter. I am running high test in it right now to make sure fuel is able to burn. I have tried different types of high test and all is the same. When the weather is warm it runs 85 % well but when it is cold out it runs in the above described condition. I checked throttle body spray with a timing light and fuel pressure and all is well. At this point I am stumped and suspect a MAP sensor but want to narrow it down before I buy components! Any help would be appreciated. The thing that bothers me is that when it is first started in the morning it runs like gangbusters but deteriorates as it warms up. That's why I suspect sensors??????? Thanks to all who reply in advanced!