If it is a factory rochester dual injector TBI, that is usually a fairly reliable system. I can tell you this much for sure though. 1)You wasted your money on the computer. If a TBI runs, it has a good computer. 2) The first thing you should check is your CKP. Crankshaft positioning sensor. It tells this motor how many RPMs it is running at, and as such is a referance for injection speed. A good way to verify this is to have someone hit the gas and bring it up through the R's while you watch. If you get a steady spray of fuel, chances are its not the CKP. if you have fluctuations, thats a common target. Also, use the Pin(paper-clip) method of computer scanning to see if its the O2 sensor. If your truck is saying its running too rich or lean, it will try and compensate, causing the condition you speak of. If it is the O2 sensor, spend the $10 and get the socket. it Really helps.