2000 GTP just got running, went for a drive, when you accelerate the car shakes, when you let off the gas and coast at any speed it stops and is smooth and drives fine. Any thoughts? It feels like a bad belt kinda shake but it'* at any speed your going only when you accelerate. Thanks

I'm suspecting a cv-shaft. Give each shaft a tug in all directions and try to twist them also.

Would the harmonic balancer do that, or would it shake the entire time the engines running?

Harmonic balancer would vibrate either way.

Look closely at the inner shaft (tripod) if the axle was extended to far one of the rollers may have come off .Checking for excess movement by twisting should help.Sometime you might see a bulge in the boot.

I had the same issue with a different brand vehicle, and my problem turned out to be the engine/transmission mounts. Hope that helps if you're still looking. Steve.

Yeah sounds like a CV joint to me. Unless your engine is misfiring under load? You didn't mention an SES light so I'm assuming it'* an axle.