Lack of power on acceleration

I had thought about the fuel pump, and also the fuel pressure regulator, the problem for me is the apparent difference in performance based on the ambient temperature and the fact that it is intermittent. Sometimes fine and other times noticeable. I will follow your advice and check the pressures on this vehicle. I need to install a fuel access point to check fuel pressures.

I should add this, it happens when I really want to scoot so if I step on the pedal expecting to just go anywhere between 1800 rpm's and 3500 rpm's this happens. I do not notice it if I just press the accelerator and want to go faster, only during a load situation, uphill or get out in traffic and go.

I edited my previous post. As this does occur under load conditions, hard acceleration and uphill acceleration. 1800 and 3500 rpm's. Is the normal range where it lacks the oomph?

1: If the catalytic converter is clogged would I not notice the lack of acceleration at all times and not intermittently?
2: Is there a tool to check for exhaust back pressure?
3: I am thinking if I disconnect the exhaust at manifold - the A/F sensors might behave differently for example make the mixture more rich seeing too much O2 and I really would not know for sure?