Whats the diff between White r4 & e-series.

[kuz400ex]

Does any one know the difference between White Bros e-series and the R4. I am talking power gains and noise levels. Torn between which one to buy!:grr

[kicken250x]

go with the e-series pro-mag it is more tuneable you get more power it looks and sounds better may be a little more( i think?) but it is worth it...