Jake brake on or off driving on flats or small hills?

JackMS wrote:
Good to know powerspec works with inline 5. The powerspec website i saw says you need inline 6 which is much more expensive.

Yes, not only does it work, but it's fully supported by PowerSpec tech support at Cummins. When I had a driver problem, Cummins logged into my computer and updated my flash memory in the inline 5 and made sure it all connected to my engine. They were very helpful.