I just installed a 19T on mine. I don't have a tach either. I don't know how it would do with a stock motor, but with the 904 it works great for me. I rejetted from 140/42 to 150/45 at the same time I installed the 19T (up from 18T)and picked up 12 MPG! Now i'm back up to 50MPG and loving it!
