Hi Andy,

I recently had a really annoying problem similar
to yours. My A15 would be fine in low revs,
but take it up to 3-5,000 and it just lost power and started missing etc, finally comming to a stop.
I discovered (after replacing all the leads, distributor, coil, points) that air was getting in to the fuel where the fuel line connected
to the fuel filter.
I had shitty little fastners, so I got proper ones that screw tight.
After that no more problems!!!!!!

Justin