Parleys Diesel sells a "chip" called the
DIGI CRTV.
It fits pretty much all ISL's. It connects to a plug on the fuel rail and changes the fuel timing. It's got a double plug on one end that allows you to disconnect the plug on the engine, plug into their cable and the plug their cable back into the engine. The cable is about 20' long and is usually mounted inside the coach. The "chip" plugs into the other end and is adjustable. It also has a "dummy" plug that comes with it. If you install the "dummy" plug, it puts your engine back to stock, like it's not there.
I believe the "chip" is used for multiple engines and has about 16 adjustment points that you adjust by turning with a small screwdriver. Everyone who has used one adjusted theirs to either "8" or "9", when installed on an ISL. Some pulling excessively heavy loads got a "Check Engine Light" when set at "9" and turned it down to "8".
How it works......the "chip" changes the fuel timing, but reverts back to stock at WOT (wide open throttle) so you don't hand grenade the transmission. It does not leave an imprint on the engine computer.
I installed one on my 2005 Monaco Diplomat. I saw a .5 mpg increase and a substantial power increase. One poster bought one almost a year before I did. I waited and stayed in touch with him to see how it worked. After about nine months and no damage, I bought mine. Several months later he put his on a dyno (Monaco Owners Forum). The chip added 52 HP at the "9" setting.
With all that said, I doubt there is a 450HP ISL (in a motor home) that is putting out 550HP. I think the person the OP was talking to is living in a fantasy.
Before the haters start in, the DIGI CRTV works and works well, at least in the older engines. When I sold my coach, I removed the "chip" because it was going to a dealer and I didn't want some buyer to get the coach and not know there were some changes. Figuring I would never use it on a new DEF engine, I sold it to a friend for his ISL. I later found that it does fit ISL's all the way through 2015. My coach is new with only 18K. I acquired another "chip" that was removed from a coach that was sold and have it in my garage. Since I'm still under warranty and haven't seen anyone running it on a DEF motor yet, I'm holding off on installing it.
