2001 Chevy Blazer service engine soon light

Have a internal engine problem. Before I spent any more money on my Chevy Blazer, I would like to know is there some way to detremine what is wrong without spending a $1000 for a analyis. I have been told it could possible be an exhaust valve burnt, bent pushrod, broken valve spring, or collasped lifter. The following things have been done: Confirmed misfire at cylinder #4. Checked spark plug and switched with know good. Checked wire and distributor cap and replaced with good, no change. Performed fuel injector balance test, all within spec. Fuel pressure within spec. Using vacuum gauge checked for stuck open or burnt intake valve checked ok, checked compression 110 psi dry and 120 psi with oil. Cylinder 4 compression on cylinder 2 170 psi dry. How much would it cost to replace or repair : bent pushrod, broken valve spring, collasped lifter or exhaust valve.