Toyota Repair: 1995 t-100, master electrician, steady decline

Question
I have a 95 t-100 xtra dx 2wd 3.4 v-6 A/T with 70,000 miles @ 4000 rpm's the engine acts like a rev limiter is kicking in, with no check engine light ever. I took it in for repair and I was told that that the rev limiter had moved,they fixed the problem, but a year later it has come back. I now know that a moving rev limiter is impossible, I installed an different computer  from Cal. and the problem remains unchanged.  I had the timing belt changed about a year before the problem occured the first time. I looked for the grounging buss as mentioned in one of your previous responses, but I am not sure what the buss looks like. I am a master electrician and pretty handy, but I have no experience with this type of issue. Any help or direction would be greatly appreciated. The folks at the computer shop told me either low fuel pressure or a clogged cat. converter.  I used starter fluid sprayed into the the engine to see if a lack fuel was the problem no real change. They also suggested removing the O2 senser before the cat to relieve the back pressure haven't done that yet. I tapped on the cat. and no rattle is that normal? I see the ground wire from the left side of the engine to the firewall it is connected and I see a little plastic square housing that has wiring going in and out over the front to cylinders, by the head and intake manifold wires from the ignition modules and going out to a sensor or something on the intake manifold one of the mounting brakets is cracked is this the grounding buss? HELP!!!!!! PLEASE!!!!!

Answer
The engine has no rev limiter.
When the loss of power happens is it a steady decline or is it a cycling condition?
Does the engine backfire or misfire?
There is a ground connection for the computer at the rear of the right valve cover see if it is tight.
If the power loss is steady with no backfiring or jerking of the engine I would check the possibility of a catalityc converter problem, it may be partially clogged restricting the exhaust.
On the other hand there could be a restriction on the intake side, check the air filter and make sure there is nothing restricting the intake air flow.