intermittent 2500rpm idle **help**

[neanderthal@ardvark.com]

Hello all,
     One of my '86 5kcstq's has started ilding at about 2500 rpm.  This problem
is intermittent and there doesn't seem to be any particular thing that makes it
happen (or quit happening).  When it starts idling at a normal speed, the rpm's
drop suddenly, just as if I had just taken my foot off the gas pedal.  I have 
checked the throttle linkage.  No problem there.  Could it be the throttle
position switch?  I can hear it click when the throttle is moved to the idle
position.  Is the throttle position switch supposed to detect WOT?  It does
not click when the throttle is wide open.  
    The other thing I am wrestling with is that over 1.5 bar on the dash gauge,
the engine runs great for a few seconds, then starts to miss/lose power.  
This problem is present on both cars.  Mods: Charlie's wastegate spring/
grounded fuel pump wire at computer.
   Given the fact that both cars behave approximately the same, I am thinking
that the problem is likely retarded timing due to high boost levels.  If that is the
case, is the only solution is to buy a computer mod. from one of the suppliers?
Any ideas/suggestions greatly appreciated.
                                          Mike Loeks
                                          '86 5kcstq   Squared
                                           Warren, Oregon