I have done some mild porting and polishing on my tsi. I took a dremel and ground all un-smooth defects in the casting (also increasing port size to my satisfaction). I did not take too much off the ports because I didn’t want to weaken the head. Then I took polishing pads and polished the exhaust port until it was reflective. I felt minimal power increase and engine harmonics changed even though the flow bench readings increased dramatically. I think it was worth it to do the work myself. I really don’t think it would be something I would have a machine shop do, unless I have the extra money to waste. There are much better upgrades you can do for less $. If u do want to go the distance…. u should also get a 4-angle valve job done and shave the base of the valve for maximum flow and sealing.