1988 80 Quattro engine trouble codes

[blarson at zeiss.com]

I am having some driveability problems with my newest acquisition  It is a 1988
80 Quattro 5 cylinder, 182,000 miles.

The car runs well until about 5 minutes of driving, at which point the check
engine light comes on and the car becomes really sluggish

when I flash the trouble codes it flashes
2142 knock sensor
1111 control unit
2123 full throttle switch
1111 control unit

The things I have done to the car so far are.
tune up
fresh premium fuel
injector cleaner (techron)
knock sensor is tight on block
Full throttle switch has continuity when closed
all fuses for computers and injection are good

Please reply directly if you have any ideas on what the cause of this problem
might be.
Thanks in advance,
Brian
blarson at zeiss.com
1988 80q 182,000 miles
1987 5kcstq 184,000 miles