Injector loom

I'm new to the site. thought this would be the best place to get honest answers.

I drive a 56 plate vrs tdi. 120,000 on the clock. engine code bmn. injectors have been replaced at around 60,000 miles.

I've recently had my injector loom replaced. the car idles perfect now. before the loom broke I would constantly get around 50ish mpg.

I think the car is remapped. boost would come in at around 1500rpm. since getting the loom replaced, I barely get 41mpg, and boost comes in at 1800 to 1900 rpm.

any suggestions would gladly be appreciated. many thanks.