I've never had problems with stock ones. But then, I always check them for flatness and true them up if necessary. The store bought ones are total junk though. I prefer old OEM stock ones. Much better metal and a lot thicker.
I totally agree. I was not having problems with a stock housing. I thought since I bought a nice new Air Gap manifold, I would buy a nice chrome plated one. That is when my problems started. Chinesium junk.
