Mk2 2007 2.0TD vRS power surges

Hi, looking for some ideas on what could be causing my power surging issue.

Happens normally only in 3rd gear on hard acceleration, been happening now for around 3months. The surging is like a lurching issue, happens around anywhere in the rev range but it's an intermittant issue, some days it won't do it, others only will happen once during boost then others can happen multiple times.

Work that has been done is a DPF delete, EGR blank and map out and a performance remap but that was mid summer, issue has been happening around 3/4months after remap, not straight after. Any ideas??

Much appreciated