P0171 Fault code

P0171 Bank 1 system too lean has thrown the EML on my Cupra. I've recently had a custom manifold & pcv delete removed & stock pcv, manifold put on with the rfd, I also had an S3 alloy end intercooler fitted at same time.

I'm presuming my map needs tweaking hence throwing up the code?

The car now has a certain flat spot when coming on boost, however I am booked into Rtech for next Tuesday

Any opinions on this? They were no codes prior to the work being done