89 TBI 350 stumbling around cruise

[jim_in_dorris]

I hear you. I am not backfiring through the intake, but the exhaust. This seems to me that it is caused by excess fuel in the exhaust , which gets hot and occasionally explodes.

While trying to find replacement heads, I looked at a lot of 193 heads. Out of the 8 I looked at 7 were cracked. A burned exhaust valve is common on these heads. Have you done a compression test.