what can cause a type 1 1300 engine to back fire on a sudden close of the throtthle from 2500 rpm and up

checked ignition timing, adjust the valves, check for compression, used to be 80psi on cylinder #2 so i replaced the head and this solved the problem, the compression on the engine is even (110-130 psi) but the problem still there, i don't think it's running too lean, what is the best way to tell?

i don't have much experience on mechanics so i don't know which other ways to look, can anyone with more experience can give me an advice what else to check, replace or repair in order to solve this problem?

thanx

Backfire on deacceleration would more than likely becaused be an exhaust leak.

Look for either rust holes in the exhaust, loose connections at the heater box join or tail pipe joins.
Check flange connection on all exhaust ports.

Look for tell tale black soot where is shouldnt be

Had this on our 1300 beetle.

As blue said an exhaust leak was fixed and it went away

i would also think that it could be something in the carby! i would check for exhaust leaks then if is still there get it serviced by a VW mechinic!!! we had the same prob and it was the needle and seats not letting fuel through etc so i would check all that!
cheers
rhys