Our 04 Allure High Cascade, built in Sept of 2003 with a ISL370 (Cummins reprogrammed to 400 HP config.) CAPS era engine that was builtin July 2003 - has 2 Stage Jake Compression Braking.
The tag is manually controlled to lift, by a button on the controls to the left, identified with Tag. Once you get above a certain speed, think it's 10mph, the tag will automatically go back down for stability.
I'd suggest you get your engine serial number, contact Cummins and ask them for what engine is in our specific coach. Most 2004 models have the next generation of ISL, with the Common Rail and Variable Geometry Turbo (VGT). While Horsepower Torque are the basically the same as far as peaks - the VGT does pump more pressure, so the HP/Torque curves are superior to the CAPS era engine. Ask them to point you at a link that has the HP/Torque curves for your specific engine, and that will help you determine optimum RPM for hill climbing.
IMO, the ISL was just at the edge of Power to Weight ratios for the 40' Allure. (Mine is two slides, so a bit less weight then those with more slides.) It gets the job done, but has very little extra reserve capacity to help in passing and or hill climbing, so learning your optimum HP/Torque curves will allow you t get the most out of those situations.
One other tip, if not familiar with Jakes. The ISL CAPS era engine, and I believe the VGT era engine also, has a redline of 2600 RPM for operation of Jake Brake. The higher the RPM, the greater the Braking Horsepower. I personally control our downshifts when going down a long deep decent, to maintain the RPM's between 2000-2300 as my preferred RPM's. I may hit 2400 RPM before I stab the brakes enough to get it back down.
Just yesterday, we came down from East to West, Wolf Creek Pass (CW McCall song has been played the last few days!!) into Pagosa Springs, CO. We maintained the 25 mph speed limit during the decent, by mostly 3rd gear High Jake (Stage 2), and a few times down into 2nd gear too. Very few times did I need to stab the brakes to slow down a bit more, to engage 2nd from 3rd on a steeper or extreme corner areas of the decent.
Contrast that with a Country Coach with the Big Block CAT C12 - C15. And they with the larger displacement engines having higher Braking HP, probably would have comfortably stayed in 3rd the full way, maybe 2nd - but if in second, suspect they would have been in a less then High Compression stage. (Some of the BIG CATS came with 3 Stage Jake Compression, and I'd bet a bigger heavier 45' say Magna or Affinity would have had no problem in 2nd Stage 2nd gear, maybe even having to give it some fuel from time to time to stay up to 25 mph
In the newer CC's, Like MR D's, the ISX would be comparable to the BIG BLOCK CATS as far as Braking HP
Allures are fine coaches. Hope this one checks out OK for you...
Best of luck,