Checking around for other things I need to take care of, and have an acceleration question. With the car in gear, I cannot rev the engine past 2500 rpm or so. Additionally, there are times (going up hills etc) when I floor the accelerator, and will be “stuck” at 40mph, or even lose a little speed.

Is this normal, or what thoughts do you have? I have replaced the fuel filter, and transmission seems fine.

In park it normally revs as high as I want it to, although sometimes it does not, and rarely when hot it coughs and dies if I push it. Once it backfired through air intake when the latter occurred. In general the issues I described are somewhat sporadic.