On my '90 NA, when going between acceleration and engine brake, while staying in gear my car seems to be a bit jerky. I'm 98% sure my TPS is set correctly, so I doubt that it's the problem. It feels like between the two, mostly on decelleration that something is clunking from one point to another, but not necessarily making noise. If I have the car sitting still, and rev the engine rapidly or let it rev and then let off immediately there is no movement of what ever it is. Is it possibly the engine mounts or tranny mounts gone bad or going bad? I usually take it extra easy going between gas and off the gas because of this problem. Anyone know what I'm talking about that could shed some light on the subject?

 

Almost forgot, if it is one of the two, how would I check? I don't have another person around either to torque the engine for me with the brake on.

 

Sounds like the front diff mount failed. Do you hear a clunking from behind you in the center of the car? Stab the throttle and let off it a couple times in any gear you want and see if you can hear the thunking. What you described is exactly what mine felt like when it went out.