Slant 6 dies.

If you have the Holley 1920, I went thru 3 bad rebuilt ones before a 4th one finally made the engine idle like a kitten. That was over 20 years. The final straw was when a newly rebuilt longblock wouldn't idle well, so figured it had to be the carburetor, despite changing it twice already. They have a sealed metering block which clogs and rebuilders don't get in there or even test the rebuild. I agree that installing the air filter shouldn't affect the engine. Figure that out first.