To be honest with you, nothing beyond stock. I'm a deisel mechanic (wait for the jokes) so all this stuff is a learning process for me. everyhting I have done has been self taught, so bear with me please. I ask these questions because I don't know, and would like to know the proper way to do things, the shade tree mechanics around here tell me a different story every F$*kin time, and to be honest I'm getting kind of sick of it.