have you considered putting an exhaust brake on it?i found a good source for info on the jacobs site on how to diagnose and adj their brake assys if it helps,,

the jap trucks use exhaust pipe brakes,work pretty good

thanks for the info about the exaust brake. I have been told that that can cause some engine troubles in the top end if not careful, although Mack did offer the "Stealth Brake " back in the 90s, but I havnt found much about it. Iv been told the jake on the mechanical e7s is a turd no matter what unless u change out the oil pump to a high flow unit, which I think requires removing the compressor and changing the oil pump drive gear, and that is a nightmare. if u think of anything let me know,