Is there any chance that you may have done something to throw the
timing off? My 83 240 Turbo was totally gutless after a timing belt
replacement and it was found to be the result of improperly adjusted
timing. The turbo still spooled up but the power wasn't there. That
also goes with the "fluttering" sound you're hearing... I think that's
detonation.
Just a thought.
Blurp
