@740GLE There are a few concerns with that. I was in a position (before I decided on Kerma for both of my diesels) to code out EGR and SCR, while leaving DPF in place. The car stunk to high Heavens, especially in cold weather. I always felt NOx were odorless, but whatever it was, once weather turned cooler, the exhaust left a very sour smell to the garage. I went back stock, smell disappeared. Of course, I feel BMW has more reliable SCR system compared to VW, since it has been trouble free for 80K miles since I bought the car in Dec 2017. I have had a few issues with TDI's SCR module, unfortunately, as mentioned above. From discussion with DPF deleted individuals, you also get some smoke. So now, you have a stinky smoking car. Will it be more trouble-free? I think probably so, but I decided having family and a child, I would rather deal with issues than expose all of us to those irritants. And believe me, I am not an environmentalist, I just could not stand the smell myself, it was nasty and it got worse over time.
Second thing to consider - EGR delete. You do not want to delete EGR completely. I agree, it is a stupid design that dirties the engine on purpose, I clean my intake annually as part of my regular maintenance with LiquiMoly Diesel Intake Cleaner. VW has a more complex EGR than my BMW. BMW has an EGR valve then EGR cooler going straight from exhaust manifold back into the plastic intake. VW has both high pressure and low pressure EGRs (fancy!). Anyways, our diesels are very efficient in terms of reduced loss of energy to heat. When my EGR was off temporarily, engine took 3 times longer to warm up in winter. I would often take a 30 mile drive and the engine oil temp needle would just be halfway to the warmed up side! You want *
adaptive* EGR. You want it to help heat up the engine/coolant/oil quickly especially in cold months, and then shut off when the car is warm. This will reduce unnecessary wear from engine running cold for too long. Yes, you certainly accept carbon deposits in intake but it is a small price to pay, especially if your EGR is open only for a warm up portion of your drive. It certainly does have its benefits. BMW with its non-US B47 engine actually re-did the EGR system to start from AFTER the DPF. That way, you would recirculate filtered exhaust instead of dirty exhaust, but unfortunately that engine never made in to USA. That is one thing I wish I had. Either case, EGR reduces combustion temperatures and thus reduces NOx. With adaptive EGR, you would increase NOx production however active SCr will adjust to take care of that. And at the end, you will still remain within VW's agreed upon limits on NOx.
So the decision is yours at the end. Kerma keeps your emissions intact but adjusts a lot of the parameters to improve their reliability. You still keep a road-legal vehicle while enjoying the benefits of a tuned car. I feel Kerma is a version of BMW's MPPSK - a road legal tuning package you can install on a vehicle. I am not in an emission state, we don't even have annual inspection anymore, but I decided my family's health is not worth the risk of jeopardy. And in the future if DPF clogs up, EGR fails, or SCR croaks, I may sing a different tune. For now, all is peachy and I am knocking on wood just to be safe. LOL.