I've been having the same issue with my 440 six pack. It will stall when it's at operating temp. It will always restart but die out again when it's put back in drive. When it sits and cools of it will be ok. I have an Accel super stock 8140C coil that's about 10 years old. It's getting real hot to the touch. I ohmed out the primary and secondary windings and found them to be within spec.. I removed it yesterday to replace it and found it was leaking oil. I havn't driven it yet but I think this is could be the issue. So you may want to look at your coil as well.