On my scangauge I had to select the more button a couple of times and it comes up with both or J??8 or J??9. It was initially on both. I changed it to the number ending in 9 and boost is now more realistic - up to about 28 -29 on a pull. This suggestion was made to me by scangauge after I sent them an email describing the problem. You might give that a try and if need be I'll go out to the RV and do the process again so I can accurately describe the process.