Here is another solution which worked for me. It has been published before
by Jim Davis, credit goes to him.

problem: idle surges when engine is at operating temperature

solution: replace a transistor in the idle control unit (behind right
taillight)
remove right taillight, pull black box on fender up and out (like a
relais), pull up black cover by carefully prying sides apart on the
underside while pulling, carefully unfold the two boards, look for upright
transistor (has three legs and a hole in the center), replace with NTE185
(available from electronics store, cost can$3.66 plus tax), reassemble and
install in reverse order

tools needed: 
Philips screw driver
small flat screw driver 
electric soldering iron

cost savings: approx. can$300 (US$200)

cheers,

Bj�rn

Bj�rn Ratjen
Mill Bay, B.C.

1987 Vanagon Syncro est alia (self camperized, TDI wannabe)
1978 VW Bulli (self camperized)
1995 Passat TD Wagon (hers)
1970 VW Beetle (son's)