04 Rendezvous cuts out on any acceleration.
 

Hi all,
Trying to help my son with his rendezvous. It cuts out on acceleration. Every once and a while, it will go back to normal for maybe 30 minutes. Then back to completely cutting out on all but the mildest acceleration. From a stop, it does well until about 15 mph. No code showing.

New muffler, new cat, new oxy sensor, full tune-up. Drained the fuel, ran seafoam for two tanks, new external fuel filter. Been to the mechanic. Fuel pump is good. I asked about the MAF sensor. He said it was good. We're lost. Mechanic couldn't figure it out. No code doesn't help.

Also, this vehicle starts and idles perfectly.

Has anyone had this happen and successfully found their way through it? I can't believe that this has only happened to us.
I'm hoping for some direction. Thank you.