We've had our fuel-injected KTM 300 two-stroke enduro bike on the dyno and found real power gains with an aftermarket exhaust system.
And now by adjusting the stock powervalve, we've found even more useable horsepower and bigger spread of power!
Note: Adjusting the KTM/Husqvarna/GASGAS TPI power valve is not the same as with conventional, carburetted two-stroke engines. The valve itself is the same principle but KTM do not recommend you change it too much from standard setting or switch the secondary spring rate on a TPI engine.
Older carburetted two-strokes and also MX models normally take a green, yellow and red spring - green being stiffer and slower to open and therefore softer power characteristic, red the opposite with yellow in the middle.
What you do with your bike is up to you but KTM, Husqvarna and GasGas recommend you seek authorised dealer advice if you think your bike is not running correctly or you want to adjust the feel of the power for trail, extreme or faster racing.