ORIGINAL: lbarnes
The Spad design states a 2000 plus rpm gain and the other 800 plus rpm gain.
There's no way you're going to gain 2,000 RPMs over a good muffler just by fitting a mousse-can.
Even a good tuned pipe will struggle to provide a 2,000 RPM gain on most engines and a MCP doesn't come close to offering the RPM hike that a proper pipe does.
Typically you can expect 800-900 RPMs with a good MCP (in my experience).