k1500 running rich AGAIN???

well, I'm annoyed. my 91 K1500 last year had a rich running problem with these symptoms:
1. rich smelling exhaust (very rich, most of the time) 2. VERY poor fuel economy
3. noticable increase in power 4. back of throttle body area had lots of buildup from puking FPR
that was rectified by installing a TBI rebuild kit and essentially replacing all the gaskets and the FPR bladder (believe the bladder was the culprit). things got much better, economy came back and it didn't stink anymore.
SOOOO...the other day I do some simple maintenance. clean the K+N filter, top up fluids, etc. next day I notice significant power increase, and figure that the filter being clean did it (not!). it seems like my fuel economy is going again....$20 cdn would get me about 130 or so KM consistently. my last fill I had to push it to get over 100 KM. Just filled up today, so will check it out....
the kicker...I pull the air cleaner assembly off to check things out. Man, what a stink!! major raw fuel smell coming from the throttle body assembly. what I saw
1. no fuel leaks that I could discern easily...fuel lines and such dry 2. all the throttle body screws were tight 3. injector spray pattern seems clean and solid 4. powered on ignition, no leaking injectors 5. once warm, the truck really doesn't smell rich on the exhaust (not near as bad as last time)
tell me guys, whats the deal? the truck starts and runs perfect. the only reason I know there's a problem is with calculated fuel efficiency and the strong raw fuel smell coming from the throttle body area. No other leaks, throttle body clean, etc....can you suggest what else to look at in this picture? If it makes any difference, my cheapo parts-store muffler from 2 years ago is now leaking....spurt, spurt spurt (I read somewhere that leaking exhaust fools the truck to see a too lean condition??) thanks for your advice!
b
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What condition and how old is your O2 sensor? Cam

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Can you explain what the "FPR bladdder is", as I have a similiar problems, 95 K1500. Just replaced the 02 sensor, still no improvements.
Thanks.

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The O2 sensor is a GM delco piece that was installed about March of last year. The FPR is the fuel pressure regulator....it has a rubber bladder inside that controls fuel flow to the injectors. last time this happened, this bladder was ruptured allowing mass amounts of fuel to pass to the injectors....what an increase in power (yay!), but sickening gas mileage (bad!)
the only other things I can think to tell you are the truck starts and runs perfect, "seems" to go into closed loop after it warms up cause it doesn't smell rich (tho it does smell rich during warmup!! think this is normal?) and the truck doesn't set any codes....
?
b
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Where's the FPR usually located and what's it look like?
Thanks.

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if you take the air cleaner and riser deal off the throttle bodie, its the casting just behind the two injectors. follow the fuel line up to the back of the tbi...the fuel line conects to the fpr. it comes off in one piece, with the upper portion of the tbi casting, but you sacrifice a few gaskets in the process....
b
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