When I press the pedal all the way down my engine will just bog down and sometimes sputter or backfire. When I say bog down it's actually not really bogging down I don't guess. I can hear and feel the RPM's get a lot higher, and I get pulled back in my seat for a split second but the blazer actually loses a little bit of momentum under full throttle. If I just stay on the gas about half way it will get up and go like a 350 with 120k can be expected to do. My timing is at 8* and I just replaced my fuel filter yesterday. I did notice a slight improvement with the new fuel filter, but so many posts on here lead you to believe the fuel filter could be the culprit for what I'm experiencing. Anyone have any ideas? Oh yea... I also run the Fuel Injection cleaner stuff about once every 2-3 months, maybe I should rebuild the TBI?