I had read all 7 pages and I see a member asked about the OBD and emissions about a year ago and he was replied by PM and there was no resolution. I was hoping by now that the people doing these tunes (presumably you and BimmerOEM) would know if the ECU can be coded to make it look like any deleted system is still functioning. Like how the secondary air pump fault can be masked with software on the e39 M5. I would think answering the emissions question is important to most buyers because I don't know many states that don't have emissions testing for cars less than 25 years old.

Regarding partial delete of hardware, I think I'm understanding that
1) DPF delete can give noticeable power and MPG gains.
2) EGR doesn't give as much power gains but will help you have a cleaner engine in the long term, but cannot be deleted without first deleting the DPF.
3) DEF system won't give any power gains but can be deleted with just software.
Is this correct?

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2012 X5 35D - EGR delete and Stage 2 tune
2003 M5 - Imola/Caramel, Dinan S2 suspension, Alpha-N tune
1990 M3 - CF Airbox, Alpha-N, Schrick 284/276 cams, VAC S2 head, full GC suspension
1991 M5 - Black/Black - stock
1991 325iX - Winter beater

Retired: 1999 328is 5MT, 1994 525i 5MT, 2003 530i 5MT, 2012 X3, 2006 325i 6MT, 2001 M5