Help Replaced everything and still crappy

92 S10 Blazer 4.3 vin.W, Stock
Problem: hard starting, bad MPG(8-10), no power(floor it to get to 55MPH), Bad gas smell when Idling, timing spark advance is jumping from 8 to 15 when running, backfires(exhaust)

I have replaced the motor(2yrs), muffler & Catalatic converter(1.5 yrs), O2 sensor & TP sensor(1yr), Battery & altenator(1yr), tranny(6mon), in the past 2 weeks I have replaced oil(Castrol 5w-30w) & filter, plugs(champion), wires(oem set), distributor(timing is set by sight, of old DISTRIB.), Dist. cap, rotor, ignition control module, CMFI(spyder) assembly & hoses, EGR gasket(EGR cleaned not carboned up, not sticking), vacuum hoses. :banghead:

Took it to Lone Star Chevy, they told me without a doubt the CMFI, I asked them to set the timing because I replaced the DISTRIB. and at first the female(no offense to the Ladies and women out there) told me that it can't be set on that truck(sealed by computer) :screwy: , waiting for truck outside she comes out and tells me it can be set but we don't have the tools :loser: , :2cents: after a few choice words (no swearing in public) :2cents: I tore up the work order on the CMFI($934), took a day off work, replaced it, and STILL RUNS LIKE CRAP, BAD MISS, BACKFIRES THROUGH EXHAUST, WHEN GIVING A LITTLE GAS(stumble, backfire, picks up power and speed a little better). :angryfire

Any Ideas?
P.S. If you go to LONE STAR CHEVY, tell Shannon I said HI!!! :evillol:

Buy a timing light! Not that this is your problem, but run AC plugs. They work best in Chevy's.
Hard starting is often Fuel pump related. May be worth trying after you list of already replaced parts!

I've got a 94 S10 Blzr 4.3 A few years back I had the same symptoms and it turned out to be my CMFI Spider injector. It was flooding 2 of the cylinders causing my to run on 4 cylinders and use enough gas for 8. I had raw fuel coming out my exhaust which I could see in my rear view mirror when accelerating using the passing gear, on high RPM's. You said you changed it yourself. I never go to the dealer, I'd suggest finding a reputable Auto Electric shop. They've been a god-send for me when I'm not sure of what the hell is wrong.

Also, I just replaced my Fuel Pump, Sending unit and Tank. The fuel pump just up and died on me. The sending unit had some issues and the tank was starting to rot out and would have had to been changed soon.

Trigger, thanks for your humor in such an awful situation. www451, thanks for the advice. my 95 is doing the same things. thought it was the pump, but its still running fine, just not shutting off.