Please Help, Need Advice about Vibration at idle

[Ghost916]

I could use some good advice, I have an 03 GMC yukon xl 5.3L. I am having a vibration that can be felt in the steering wheel and seat but only at Idle and in drive. Its Not my TB, I have had the TB cleaned, Fuel injection flush and engine mounts adjusted. My RPMs is steady and the truck runs great, very smooth when driving but vibrates when I get to a stop. The vibration gets a little worst when I turn the AC on (driving me crazy). Has anyone encounter such an issue? what is the fix? the dealership said the next step would be to install a flex pipe in the exhaust system, does anyone know what that means? Please, any advice would be great.

[handy1219]

Hi. Have you noticed the oil pressure in your engine during these shakes?? Good idea in this case to check the e eight cylinders, to know what to do...
Is it flying down & up? or it is still the same and if so - what is the pressure?
How many miles are there on the truck? R U the first owner or bought it from some one? Any other problems, like the high temperature of the runnig engine?? Please reply.