I just added a Wb e-series and a K&N with no air box lid and rejetted. How many tuning plates can I run with out having to re-jet or tune anything? It is for a KFX400

 

On the 400ex , it was said 3 plates are the same back pressure as the stock muffler. Do yourself a huge favor and jet that quad so you can use the pipes power. If you don't jet and use the pipe, plugged up, you have thrown $$ out the window.