Bad tune after bad ECM failure

[Kenworth2024]

I own a Peterbilt with a Cummins ISX2250. About 5 years ago I had a remote tune and @m*m^2 delete done on the truck. The truck ran great until last week when I started getting multiple fault codes. A local mechanic diagnosed it as a bad ECM, so he replaced the ECM and installed his own tune.

Since then, the truck runs terribly. It has very little power, doesn’t pull like it used to, and overall performance is much worse than before the ECM replacement. The truck was running fine prior to the ECM failure.

Looking for some help. Thank you