99 3.2 Code P 0420

Catalyst 1/1 efficiency below required level.

Other than maybe not passing an emissions test, any harm or potential problems in driving with this?

I'm assuming this bad cat was caused by driving for a bit with 2 bad coils and a bad intake gasket.

 

no harm except emissions. it is just like having a straight pipe. the only annoying thing will be the check engine light probably will never go off.