Githes

I just have the one wing nut. It is a long rumble of pops.

I have an 86 720 that I have recently replaced the head gasket in. Yesterday, it started to back fire only while down shifting to slow down. I just replaced the O2 sensor this morning and that didn't seem to help. Could this be fixed by replacing the muffler, which I intend on doing tomorrow, or is it something else? Another problem that has risen is a loss of power when in fifth gear. Are these two problems related or are they two separate issues?