Chevy & GMC Vans

I'm in need of some help/suggestions on my van.

I have a 2000 Astro RWD. About 205,000 miles on it. A fresh transmission rebuild as of about June or July.

Symptoms:

Runs ok in idle. Seems a bit rough to me but scan tool shows high 500'ds (580ish) at idle. When trying to accelerate normal or hard. The van seems to be bogged down (almost like something is plugged) and almost not want to shift to the next gear. It will shift to the next gear. But it is a lot longer of a process and seems to be rev'ing very high before the shift.

Also the van sometimes when wet will stall out or not start

Side Note: The van did seem to not run quite as smooth as it is now. So I seafoam through a vacuum line and let it set for a while and ran through it as the can suggests. Now seems a bit smoother.

Really I can only get the van to the 30-40Mph range before this shifting type thing is to the point I feel like the engine is going to blow up on me.

I have been trying different parts as common things that I know go bad (don't we all) which I will list below.

Parts Replaced:
Transmission - Complete rebuild from a shop in town. Done around spring and then again about July to August as there was some sort if hard shift issue coming back. But not the same as the issue mentioned above.
Distrubtor cap (AC Delco) - had whitish and brown charing on the points on the inside of it.
Distrubtor rotor (AC Delco)- why not I was already there.
Fuel Filter (Fram) - didn't remember the last time exactly and knew it had to have a good 15k miles on it.
Front left caliper - mechanic said that this was causing the running/plugged issue. However now the right front is pulling hard.
drivers side rear brake line - I know has nothing to do with this, but thought I'd give all the info.

I have recently replaced (spring time-ish) the cat as it was getting bad causing stalling issues.
Front brakes and rotors - end of last summer
front wheel bearings - end of last summer with the brakes.


So my question is, what should I try next? I feel like I have checked all the vacuum lines, and they look good as I replaced them when I bought the van 3 years ago, replaced the cap and rotor. I also replaced, I don't know why, the front left caliper. Replaced the fuel filter. Checked the fuel pressure and am getting 60-62 when sstarting the van and about 56-58 when van is off for a while. I'm at a loss as to what to try next and of course this is my primary work vehicle.

Any help or suggestions would be greatly appreciated.

Thanks,
Nathan

I would try cleaning the maf sensor if it is dirty and not reading the right amount of air going in that can cause it to bog like your saying. Have you run a code reader on it? The other suggestion I was going to make was the cat did you get them all replaced? If you only did one you could always try loosening the clamp infront of the cat and take it for a drive to see if it runs better when it can breath.

What about plugs and wires? Any MIL codes? Maybe unbolt the muffler/tailpipe just after the cat and see if it runs better. Maybe the muffler is plugged. Another thought is a worn out distributor gear.