Did their job right.........I should think so as , according to the OP, it was on the rollers for over 14 hours, fine tuning it. I did drive it before the 20G was fitted and it was fun to drive.
Dave, ask the to compare Air flow readings (MAF from your old maps on the VF and the 20G to see if there has been a comparable increase in air flow to comfirm the turbo is throwing in loads of air.
Also ask them to use a BRAND new W/B Lambda sensor to confirm the mapped readings are correct and not an iffy sensor creating an issue (more straw clutching!)
Russell