I always thought a back fire was usually electrical and not fuel but
what do I know.....I had a mallory on my 235 and the truck would act crazy at times.. it would bog down, then run fine for awhile, then at hiway speed it would drop down to almost nothing and start up again, it would sometime back fire, etc, but ended up being in the electronic module....

Redryder pix
My Hotrod
A veteran - whether active duty, retired, national guard, or reserve - is someone who, at one point in his or her life, wrote a blank check made payable to The 'United States of America', for an amount of "up to and including my life."
I am fighting cancer and I am winning the fight | Pain is part of life; misery is an option.