when i get on it hard and shift i get a popping sound in the exhaust like gas blowing up, not sure why its doing this, it has been since i got it months ago and feel like that my power loss is part of this, could this happen with bad spark plugs and maybe there causing unburnt gas to enter the exhaust valve, also i was using 93 and down graded to 89 to see if it would help should i go down to 87, any help would be nice anyone ever had this happen, should i do a tune up like plugs and wires??????????