Hjigh speed power loss (different)

[jerry.carter@shaw.ca (Jerry Carter)]

I have a problem. My car will fly up to 4000, then just stop accelerating.
I'll let off the throttle and switch to second (I'm not thinking that it's
the clutch on mine, 'cause it's an auto) and again, fly up to 4000. after it
kicks into third, I'll get power out of it up until about 2500 when it just
starts slowing down. if I let it idle for a few min. then I get the power
back again, or if I drop it into nutral I can pin the throttle and usually
the car spins up to about 4000. if I pump the throttle, after about 8 pumps
I can get her to redline again, and I have power back, but that's just a
waste of fuel. I've let it get as bad as it can get (just so I could see how
things were) and pulled the sparkplugs, and they were black. I pop them back
in and let her run a little bit and pull them out again, and they're clean!
Makes me think that my mixture is set wrong, but if I lean it out at all
(the idle mixture) then the car will die. if I make it run richer, then the
problems get worse much faster.

I'm wondering if there's a high speed mixture setting that I can mess with.
if there is then maybe that's my problem. (I've probably messed with it and
not known what it does, and not thinking never gone back to it) I'm also
thinking that it might have something to do with the fact that I still
haven't cleaned my airbox yet. Time, funds, and general drive have not been
on my side lately.
_________________
Jerry C
'81 Mk1 Scirocco