Its been awhile since I've posted but I'm hoping someone has run across this problem before. My 99 jimmy runs and drives great but I noticed that when its sitting there idling it sound like its running a little rough and the exhaust smells really rich and the gas mileage isn't as high as it should be (around 13-14 mpg) I never get black smoke when driving. I recently did a fuel injection pressure test because i suspected the spider assembly of being faulty buy the fuel pressure is right at 60 psi and it held it there for about 6 hours before falling.

The spark plugs are brand new and the old ones weren't fouled up and didn't smell like gas at all. The only code I have is for catalyst efficiency low but thats because i have a magnaflow hi-flow cat. I've monitored the o2 sensors and they all look fine. I'm stumped.