hello


Suggestions:

I believe that a bad ECT sensor can cause a jumpy idle , until the vehicle warms up a bit.


Vacuum Leak:
from reading up on the forum, common vacuum leaks on these engines occur at EGR valve(tends to stick open) and Purge Valve(also tends to get stuck in open position) both are internal leaks, making them more difficult to find.

see post #1 , does that sound familiar:
http://www.peachparts.com/shopforum/tech-help/258527-what-world-wrong-my-94-c280.html


ETA:
have you inspected the throttle linkages and springs, its possible that you may have disturbed one of the links/springs during ETA installation. have you made sure that the throttle plate moves freely?

good luck