Hello Community, (Note: this is my first time posting on a forum.) I have an 86 Mustang 5.0 that has been running with out any notable vibrations. Over my holiday brake from school I did some engine work and never touched any aspect of my drive line. Now after the my work there is vibrations toward the top of each gear, mainly in 5th. The vibrations mainly occur when accelerating and completely stop as soon as I push in the clutch peddle. I removed my drive shaft and had a drive train shop check its u-joints and straightness. They say it is in good condition. My motor mounts and transmission mounts look to be fine and there is no slack in the transmission tail housing bushing where the drive shaft yoke inserts. I think the vibrations are from the engine because when I apply more throttle in 5th I can see my upper intake manifold violently begin to shake side to side (my car is currently hoodless). Here are the main modifications I made just before the vibrations started. -New SVE radiator and electric fans. -PVC to catch can / breather. -Upper/lower mountaineer intake manifold and throttle body swap. -Removal of all smog systems, and vacuum reservoir. -New spark plugs and distributor cap and rotor. The car sounds different from before the work. It now has a slight clunking sound. I appreciate the help!