you can lose power with a bad tune. not pointing any fingers but i've seen it happen with other tuning companies. they may be great but every now and then they make a small mistake that throws everything off.
2008 M3 Sedan + TestPipes + Tune [sold]
2012 CLS63 AMG + P30 Performance Package
2014 M6 Coupe + AMS Downpipes + KW V3