97 GA hesitates-bogs down on acceleration

[19k40rocky]

I have a 97 Pontiac Grand Am w 3.1 engine that is my son's college car. We recently rebuilt the original engine and put it in after having a 99 monte carlo 3.1 engine in it's place and it had a head gasket problem as well. Just before we switched engines my son was noticing that it would kind of hesitate under acceleration from about 1500 rpm to around 2000 rpm especially when it was wanting to up shift. I figured it would resolve itself with the engine change. It did not. It has now gradually gotten worse. My son drove it to Liberal about 4 hours away and he stated it was worse and especially when you would get into overdrive it would drop down to around 2000 rpm then start sputtering or loading up or just being dead then would down shift to 3rd and try to clean itself out and speed up and then up shift to OD and do the same cycle again. I drove it back and kept it in 3rd gear and seemed to run fine at 2500 or higher. I also had to go thru low, and 2 and feather it up from a standing start. It idles fine as well. I thought it might be like one of the saturns I had which ended up having a plugged Catalytic converter and a bad coolant temp sensor. This morning I did a test hole and it made no difference. I tryed a different coil pack/ESC and it made no difference. I cleaned the MAF sensor and no change. The fuel pressure is 41 then 38 when idling then 43 when remove the fuel pressure regulator vacuum hose. I also changed the fuel filter. I was kind of ruling out the tps, iac, and egr and water temp sensor as those were part of the other engine when I put the other engine in so they are different and I am assuming they must be good. Plugs and plug wires are new as well. It has not thrown any codes. I did notice that when it is just in park and you press on the accelerator to rev it up it only will rev to 3500 rpm and will shut down like a rev limiter is kicking in and just do a kind of surge thing. my saturn did that too and it was a plugged cat and when I knocked the biskit out of the manifold on that car it stopped. I have already got that ruled out though. Any ideas as to what to look at next? I had tried to get an answer from a pay site but they apparently want to touch the problem. Any and all help I would greatly appreciate as I am getting really frustrated with this thing and am running out of time.

[19k40rocky]

correction-pay site DON'T want to touch the problem

[Tech II]

OK, engine at normal operating temp....if you rev it, it is ok, until 3500(yes, the PCM has a rev limiter built in)......

Now from a dead stop, in "D", if you lay into it, does the engine top out at 3000 and the car refuses to upshift at all? If that is the case, now from a dead stop, very lightly accelerate.....if the car slowly gets up to speed, and shifts though all the gears, then the exhaust is plugged, be it the cat or further down the line.....sometimes a test hole is not big enough.....removing the pre O2 sensor or creating a gap at the ex manifold and ex pipe, is necessary....

What is puzzling is that no codes are set.....

[19k40rocky]

I mashed it and it goes thru the gears and well beyond 3000 rpm. I ended up cleaning out the cat and made no difference.