I've got P0401 and P0171 stored (along with the pending P0170) on my '97 Civic HX. It's been having EGR issues since I bought it in feb. I cleaned out the EGR port and valve thanks to the detailed article by Delbert Brecht from hondacarforums.com which took care of code P1491 but several hundred miles later the system lean code (P0171) came up.

Not sure where to start with diagnosing the problem.

I know it's quite likely a vacuum leak. I've sprayed the EGR area with carb cleaner but didn't hear any RPM surges.

I listened to the fuel injectors clicking using the "long screwdriver" method

That's about it.

I don't have the resources to do the more specialized tests that are explained in the service manual.

Other than the CELs the car runs like a charm, great gas mileage, idles fine. The engine output surges very slightly when cruising at 55mph. Some people have told me to just forget about it, but I'd rather not have the CEL on to nag me all the time.

Any advice of where to start would be greatly appreciated.