1969GTX

I just rebuilt the top end and now it starts and idles fine but at speed it cuts out then goes like a bat outa hell for a few seconds then starts cutting out and looses power. If I run it just above an idle for 10-15 seconds it seems to clear out then goes like mad again. I also noticed that the right exaust gets hotter than the left. You can barely touch the right and can almost hold the left. I am at 7000 feet and it is pretty much stock what jet should I run?