code 91 back again

i changed my o2sensors and the code 91 went away and i did the koer test today and it came back up,my book says it could be fuel pressure out of range or injectors out of balance,but i am confused code 91 says lean but my car seems like its running rich it smells like gas bad,that is the only code it is saying with the engine running but with it off it says 11 no faults,anyone have any suggestions?

yea it has an off road pipe on it,but i dont understand y the code came back up,it went away then came back.is there anyway to check my injectors,and should i get a new regulator and run like 30lbs instead of 35 (stock right)?my car seems like its gettin too much gas and missin at idle i changed the plugs bout a month ago but i am goin to again and i have a new cap,its not surging or anything,i have changed alot of sensors that i was getting codes for and they went away but this one came back,the only code i got after i changed the 02sensor was 44 the smog b/s but i dont need it.any help that i can get will be good.