I've never had problems with the chrome peeling after porting. Just go slow so that you don't take too much off, (check often), and make sure to lightly chamfer the port edges so that they don't damage the ring and/or piston.

To realize more benefits, you are really going to have to add more muffler outlet area. Hopping up an engine is a coordinated effort, and doing one thing without attending to another leads to disappointing results. I once bought an aluminum after market muffler for one of my Homelite 30 engines. It had two tubes, but the outlets were about 1/8" smaller than the home made muffler I had been running. The engine lost 400 rpms....

The object is to get as much air to flow into, and out of, an engine as possible for max power.

AV8TOR