The last step is having a shop run a smoke test for you with an actual smoke machine. Should cost between $100-150. They'll tell you exactly where your leak is. Of course if you don't have a leak, it could be you happen to have multiple clogged injectors, but do you have a misfire?
Whatchya think behlinla, could he have a clogged injector on both banks without getting a misfire code?
Oh, and OP
, did you verify that you still were running rich? Did you check the fuel trims, or did you just pull the codes? Did you reset the codes after replacing the pcv
valve/elbow assy? Just curious if you still actually have a problem. Sorry I didn't notice this thread earlier. Can I change the name of it for you to something like "p0171&p0174 mystery"? That would get more people responding to it as well. I won't do it without your permission though.
Could just go ahead and replace the EGR
gaskets, not very hard of a job, just take the vacuum line off the top, remove the valve, new gaskets, torque the bolts to 15-22ft-lb according to alldata for a 99 vulcan. The tube that goes on to the exhaust is 26-47ft-lb (if it matter, sorry not familiar with vulcans).