My truck(87 K5 blazer 350TBI) had a missfire under load. It would do it from a stop or when making a turn. I was checking things to see what it could be. First thing I did was replace the fuel filter. It was dirty but not that bad. It didnt fix the problem. I was told to check the coil. I replaced the coil and it didnt change anything. However I did notice the dist. was loose, so I checked the timing. It was off about 10-15 degrees. So I figured that has to be the problem. I disconnected the brown wire to set timming correctly. I set it at 0 like it says, and the truck runs fine with the wire disconnected(check engine light is on now due to the wire being disconnected). When I plug the wire back in it runs rough, stalls, surges, and even has a hard time starting up(acts like timing is too high). I disconnect the wire and it hard starts, then cleans out and runs good. The only problem is it detonates under load(like if the timing is too high, but I know the comuter is in limp mode so it wont adjust the timing properly). What do you guys think it is? I also tried replacing the map sensor, cap and rotor, module in dist). Help I need my truck going so I can tow my firebird to a race coming up.