Whoever said u can't put a plate in an egr motor is full of BS. U can put a plate in almost any P-Pump.
Okay, we are talking California here, so here is what u need to do. Buy an out of state intake manifold. I get these for $60 new. Its new pretty aluminum and is almost twice the size of the Egr one. Next, put a copper or steel block off plate in between the egr tube and ex. manifold. If ya want to make it killer, then go buy an ATS manifold. Lets face it, your stock manifold is gonna shrink any way. Also, u can go to Cummins and buy an ex. manifold for a 94-95 Cummins, which had no EGR. I believe EGR started in mid 96. Those manifolds are $130 through Cummins. Okay, now that the EGR is out of the way, it would be a good idea to up the timing on the CA trucks. Most were set at the factory at 13 degrees. The plate u need is a 6 plate or a 5 plate if u don't have GOV. springs, if u plan on running Gov. springs then buy a 10 plate. It is a good idea to cut the cat out or hog it out.
THERE IS TESTING IN CA! Most of us are lucky, but on the grapevine they do pull over ALL diesels at time and smoke test them. They put a big can at the end of your exhaust. The way to get around this on Bombed trucks is to install a Vallet switch which cuts the boost going to the AFC and limits Gov arm travel. U'll pass with flying colors, no problem. If anybody asks you, . . your truck is out of state rig when u bought it. And u can put a plate on a CA truck, even if u keep the egr tube on.