I have a 89 Crx with the obdo DOHC ZC and I'm having problem with it running lean
Anyways I was checking a few things and my buddy came over and wanted to see something so while my car was idling he pinched off my fuel return line with a pair of pliers and it was almost instantly my wideband gauge was reading perfect 14.7
Any ideas?

 

You could put a fuel pressure guage on it and pull the vac line it should change the fuel pressure I think but not positive on that

 

correct son2beho. w/ vacuum you have 38 psi, w/o you have 42 psi.

it's not just about pressure. you can have a flow issue, in terms of not delivering enough gallons per hour or whatever. if your filter is plugged, pump is worn, etc... restricting the return flow can make it seem all better. sadly there is no easy way to gauge how many gallons you are delivering - all you can do is disconnect the rail feed and run the pump for 15 min, then measure how many liters or gallons you pumped in those 15 min. i, however, don't know what the delivery rate for a stock pump actually is.