fuel consumption AND cold start AND rough idle

[yurple at hotmail.com (Mark Malowicki)]

  My '83 Scirocco 1.8L has been having a few problems lately.  It started 
with hard starting when cold.  I checked the cold start valve, thermo time 
switch, and aux air reulator, and they all appear to be working fine.

  Then, I started having an intermittent rough idle problem, where it would 
drop down a few hundred rpm, then recover, then drop, recover, etc.  It runs 
fine otherwise, it's only idle that's rough.

  AND THEN, I noticed my fuel mileage dropped way down -- from ~33mpg, to 
23mpg.  I rechecked the cold start valve to make sure it's not leaking when 
warm, and it doesn't appear to be.  I pulled the plugs to see if one of the 
injectors is stuck open, but all four look the same -- electrode itself is 
light milk-chocolately, with black soot on the rest of the plug.

  Any suggestions for how to troubleshoot this?  Could it be the fuel pump, 
or warm-up regulator?  I checked the resistance across the warm-up 
regulator, and got a good 16 ohms.  Could that cause all three of these 
conditions?