Well. I got the codes. You are right, 171 and 174. I heard some sucking/hissing and there was a vacuum hose amiss. That fixed some of it. Then I could still hear vacuum leaking around the driver's side plenum, just on the seam where it meets the throttle body. Gasket sealer did not stop it, nor did torqing it down more. So, I guess I'm stuck removing the plenum and puting on a new gasket. Right??? Is that tricky or a straight forward job? Thanks.