My suburban vibrates or misfires under light throttle @ different speeds between 40 & 55 MPH.

Lean on the throttle or manually shift into 2nd or 3rd mitigates or stops it completely.

Start, idles, and runs fine above or below this range.

I've cleaned the MAF & TB w/MAF cleaner to correct recent a low idle/stalling problem - fixed that, but the vibration/misfire persists.

thanks in advance, Tony