I have a 91 TBI setup on my 350 SBC. My problem is on a cold start the engine will fire and idle really low it will not rev up like it should and stay at a high idle until warm. If I turn it off and re-start it will rev up and idle high like it should until it warms up. Some days it won't do this and other days it will. My fuel pressure is 12 TO 13 Lbs, There are no trouble codes stored and the TPS voltage is at .55 volts. Once warmed up the engine runs great.

 

Well since no one would help me here I eventually figured out my problem. problem number 1 was the fuel pressure gauge I was using was giving me false readings (low) Problem number 2 once I fixed problem number 1 was my fuel pressure was to high about 16 pounds. At start up the high fuel pressure caused a rich condition. When I originally rebuilt the TBI unit I replaced the regulator diaphram. Well the new diaphram seat was longer than the old one which in turn applied more tension on the spring which in turn raised the fuel pressure. I replaced the new one with the old one and my problem went away. The fuel pressure is now just under 13 pounds.