Confirming potentially bad cats?
I'm working on my girlfriends 03 ram1500 4.7 with the 4 speed auto. 271K miles on the chassis (including the cats) but it's got a fairly new engine and brand new trans. The engine runs great, really smooth at idle, doesn't throw any codes. When in drive it loses power as engine rpm increases, and can't get past 3500rpm, in neutral it revs up to redline seemingly as it should. I noticed that the bank 2 long term fuel trim was maxed at -7% on my code reader data stream, which I believe would be leaned out? I hooked up a vacuum gauge and it pulled a good vacuum at idle, and sustained a vacuum at any rpm in neutral, I tried putting it in gear and it kept a vacuum until I stood on the brakes and revved the engine up to 1500rpm ish (putting a heavy load on the engine) and then it not only lost vacuum pressure but it built up positive pressure in the intake. To me, that means there's likely an exhaust restriction that is only presenting itself when there is a load on the engine, but before I have my girlfriend spend all the money on new cats I want to be sure, so I'm asking for advice. Does anybody have any other ideas of things that could be causing that specific problem set, or any thoughts on whether or not the engine building positive pressure in the intake when under load but not in neutral could be caused by bad cats?
Any advice or thoughts or $.02 is appreciated.