Listen and feel for exhaust leaks with the engine running, especially around the exhaust donut between the exhaust manifold and the head pipe. Even if you can't hear anything, try tighteneing that connection. This may clear up your exhaust popping.
On these low compression engines, you may never get pinging on todays fuels, but if you are too far advanced, the engine will surge at cruise and will kick back against the starter.
