Toyota Repair: 97 4Runner SR5 Limited 3.4 V6, mass air flow, mass air flow senser

Question
Ted
My wife's 4Runner has lost power. I replaced the plugs ,air filter and wires from the Toyota store. It didn't help. I replaced the catalitic converter with an aftermarket unit. It showed a small amount of back pressure on the gauge  at the muffler shop. It didn't help. I took it to the dealer. They cleaned the injectors, checked the timing belt ,which had been replaced 32,00 miles earlier.They adjusted the trans shift points. The tech said he could not find any problem. He indicated that there were no codes on the ecm. Since we got it back it gets approx 10 mpg and runs poorly. It hesitates just like it has a restriction. I have removed the air filter and ran it very hard with no better results. The Toyota tech adised the mass air flow senser could be at fault without setting a code. He is a long time tech and he said he could not find anything mecahicly wrong. The check engine light does not come on even after running the P out of it. WIFE NOT HAPPY. Please help!

Answer
The MAF will trigger a check engine light,so that's not the problem, all monitored systems will turn the check engine light on if there is a malfunction with any of the computer input signals, the only thing I can think of at this point is that there may be a loss of fuel pressure, have the fuel pressure tested or maybe replace the fuel filter first and see if it helps, it's located underneath on the floor panel under the driver's seat near the left frame rail.