Finding out the injector size is difficult. Do you think ESS or these tuners want to release their secrets and hard earned R/D. Gains from stock exhaust to catless are approx 20-25 whp. Gains from 535 to 575 pulley only are minimal. I saw approx 15whp. You would get more from upgrading to the 575 kit because the car is then tuned for it and the injectors are different. IMO - if your upgrading from 535....just go to the 600 or 625.
E92 M3 DCT...Powered by ESS VT2 650/DCT GTS Software/Aquamist HFS-3 50/50/Morr /Toyo R888's
ATCO RACEWAY: 10.65 @ 131.79MPH 1.725 60FT
(Stock ESS 625)