After more than a year driving automatic, going back to 10 speed manual...

snowwy, a CNG engine does not respond to throttle inputs the same way that a diesel fueled engine does. With a diesel, as soon as you move the throttle in either direction, your RPM begins to change instantly.

The CNG engine has a throttle plate, electronic fuel controller, one injector, and uses a gaseous fuel, not a liquid like diesel. You can't just toss fuel into the engine like you can with a diesel and expect it to burn. The computer has to get the fuel mixture JUST right for the operating conditions at that moment. It also has to account for the time it will take for the fuel to enter the engine once it's injected into the intake air stream.

That's a bit of a complicated explanation, but the reality of it is that when you 'mash the gas' on a CNG truck, you might get the result you want, and you might not. Same with letting up on it. Sometimes the fuel controller will hold a small amount of torque on the engine so that the turbo won't spool down too quickly and cause a backfire. Which means that you're not going to be able to float gears as easily.

A CNG powered truck is a whole different animal compared to a diesel.

I actually did put about 5K miles on this truck before it was mothballed for quite some time while Cummins, Volvo and Agility worked through whether or not a design flaw (and whose design error) caused one of them to burn to a crisp while under load. Those issues were resolved a couple of weeks ago, and I got the green light to drive it again.