I cant speak for the other but Mark at south west in car tech is fantastic and really knows his stuff.
He charges around £300 for the custom map and will dyno your vehicle on his rolling road to maximise performance based upon your cars specification (mainly airflow).
I've been up there quite a lot these last couple of years (actually after each major mod) to adjust the mapping. Everyone has there own approach and take on intake, airflow and such like and mark will advise accordingly, making you aware of everything you may/may not know already.
Essentially, the map is a custom code and you are not limited to a set level of performance found in many other maps.
Mark, if i recall correctly, is a graduate in automotive technology (or such like) and is incredibly knowledgeable.
Personally, I cannot recommend him highly enough and even got my old man to take his BMW x5 sport down for a map. His 4.5 litre m sport diesel now puts out 514lb of torque...incredible!
Funnily enough I'll be there Wednesday as he want to dyno my s3 pre and post a new custom tip.
I also call him prior to any mods to asses pro's and cons and in doing so i probably do his head In...but he's always willing to help.
Infinity exhausts is also next door and also worth a visit too if you ever fancy a stainless exhaust at the same time. Martin runs/owns it and his products are immense too for very competitive prices. That's were I got mine from too.
If you do speak to mark, say that James from greenwoods recommended him.
Good luck with whatever you decide.
