I had someone tell me a bad erg valve on a lt-1 could cause combustion gases to enter the cooling system, I haven't heard of this but I'm not a mechanic, is this true?

 

Incorrect. The EGR valve is bolted to the intake manifold, and the exhaust gas path flows directly into the intake manifold, using the same holes in the intake runners as the idle air. The LT1 intake manifold is totally "dry" and has no coolant passages at all. No way the exhuast gas could get in the coolant, even if the valve is faulty.

 

I'm about to change the gasket on mine here on Thursday evening.

Quick question on that. Could a bad gasket or the part itself cause the car to idle rough?

 

Yes a bad egr valve could cause rough idle.