i have a 01 5speed 2 wheel drive 24 valve as far as i kno its completly stock but i am having trouble with power issues around 2000 to 2500 it loses power then around 25oo it picks back up iv changed oil air and the fule filter and it did not help im not sure what else to truy and this bein my first cummins kinda new to the whole thing so any advice would be verry apreciated

You need to do an APPS RESET. Also, you need to start looking into getting a new APPS, Timbo APPS are generally used by most on the sites.

Start by checking for trouble codes. You can turn the key to the on position without starting, then off, on, off and back on and write down codes that scroll across your trip readout. Or you can use a code reader. Let us know if you have codes and what they are for better troubleshooting.

I always start with 2 things. 1. Fuel pressure (Idle and WOT at highway speed)2. Error codes