I'm sure that you will notice a little diference. Taking the lid off will allow more air in causing the need to re-jet. I would suggest modifying the stock pipes end cap. That will give you the noticable gain. As far as the CDI is concerned I opted to go with that after a couple guys said that you hit the limiter very quickly after adding a pipe. Not needed if you don't mind the limiter.

For more info on the Modded end cap ask Adamsbad650 or I believe buttfungus, I think they are the end cap pros.