I have been driving around with the plug laying out because I could not find where it went to, no CELs and no issues after my head gasket change (except crappy mileage, 20+). I found it today and it is the back plug on my DX manifold. Is this the fast idle control?

I also did a compression test today with the motor cold (I know) 152 140+ 150 150
with 227,000 on the clock. Its my beater so It should last long enough for my Integra to be turboed, what do you guys think?

 

if the sensor was going right into one of the runners it would most likely be the IAT (intake air temp) sensor, if it was into a unit that was bolted to the manifold than it could very well be the fast idle valve.