Well to start with it was originaly a 5.8L f150. i found out earlier this month that it had a 5.0 in it when i went to put a new motor in. When it is in park or neutral the 5.0L randomly "sputters" (like a miss but not as hard). i held a piece of paper to the exhaust and when it sputters is sucks the paper in. it does it at idle andwhen you rev it slightly and hold it there. it does not do it in any other gear. this is a remaned 5.0L long block from O'rielly's, it only has about 900 miles on it so far and its done it the whole time. i put on an MSD cap, rotor, and coil and Accel plugs and wires, i got the timing at 15 degree's. im running headers and no O2 sensor, no smog pump or any of the crap that goes with it, some one before me did most of the removal. the old 5.0L i took out did this too before it put #6's rings in the pan. so i don't think it has to do with anything i removed. the truck has great power for a basically stock 5.0, i can put the E4OD in 1st and mash the gas it will spin the tire (open diff) with out touchin the brake. this is a 91 F-150 2wd ext. cab, 8ft bed - its a boat. it just sound like crap at idle and i don't think its right.
-is it possible that it still has a 5.8L computer?
- the O2 sensor was in the old exhaust with the old motor, so i don't think thats it

i know thats a lot of info but trying to describe it with out playin 100 questions