misfires on 1990 Cadillac Seville

My 1990 cadillac Seville will miss and backfire causing my muffler to blowout.i have have changed dist. and cap,dist.plugs,wires and coil.

1 answer
Check your timing. Make sure that your timing is correct, also I would check the timing chain or belt, and make sure that it is not slipping causing your timing to come off.