More HP out of my 318

Headers make a big difference, however, there not going to set the world on fire. Headers make the biggest difference on an engine with that has been hopped up more so than a stocker.

You never mentioned what cam is in there now.

According to a buddy of mine, the exhaust valve should have gone to 1.60 and the intake would probably have been better left stock, but that is also build depedent. The 1.88 installed isn't the end of the world and not a huge issue to cry over.

A 650 is a good size. The engine probably isn't useing it to it's fullest capicity. Again, a build dependent item. Also driving style.