Toyota Repair: 89 Toyota PU excessive fuel pressure, air flow meter, fuel pressure regulator

Question
Couldn't figure out the problem so took it to a repair shop not the dealer.  It's blowing black smoke, hesitates at speeds under 70 and uses excessive fuel. They replaced the fuel pressure regulator and the front (Main) 02 sensor and it made no change to the problem.  I have checked all sensors such as VSV, TPS, and air flow meter and can find no problems.  everything is orginal factory with 215,000 miles and this is the only major problem I have ever had and can not figure it out?  Maybe the ECU is bad?  never had an engine light but checked anyway and get a 51 blink I do not have AC.  Any Ideas?  I guess I should go haead and change both 02 sensors anyway as the guy put back my old parts and didn't charge me.

Answer
Well, the problem here is that I don't know which engine you have (V-6 or the 22R) Let's assume that you have either one for a minute. The Air Flow Meter is what energizes the fuel pump on the older model TCCS systems. You say that you tested it, but what test did you perform? Code 51 does not only apply to the AC unit. Throttle position circuit, sensor, neutral start switch and circuit and the ECU are all included in this error code.If you say that you have performed all the tests you say you have, the ECU is an expensive possiblity. I would recommend you obtain a wiring diagram from your local library and trace all the circuits in question before you commit to buy an ECU.