Top End Miss

Hummmmm....gear change alone would not make it pop out the exhaust if thats the case.

Hummmmm
Fuel system good..
Ignition system good..
Valves good..we think..
Only thing I can think of you could have messed up back there while changing the diff. is
Yu pinched off the fuel line enough to hinder it...Or yu pinched off the exhaust...
Other than that, I just go blank.... Unless a grounding or a power issue accrued?

Boy what a stumpier!!!!!!