This is what i found about the diesel smog test in CA and it should be absolutely no problem for a stage1 tuned car to pass with flying colors. The tune disappears when the DDE is flashed with ISTA or other BMW tool. I dont know about the other companies, but with us the re-flash of the DDE will be absolutely free for life.

"California certified smog check stations are allowed to perform a diesel engine smog inspection if they possess OIS Smog Test equipment. The diesel smog test will not include the emissions test portion of the regular inspection. There will be no tailpipe emissions inspection either.

Diesel cars and trucks are not driven on a dynamometer during the smog test either.

The diesel smog test will focus on a visual inspection of your vehicle's emissions/smog components, a system check of the On Board Diagnostics (OBD II) system, a visual smoke check for excessive black (carbon) smoke, and an EVAP functional test. Diesel cars and trucks which fail the diesel smog test will have to get their vehicles repaired at a diesel vehicle repair shop before retesting."