i just picked up a Cummins engine manual covering 12vs. I dont know why but the manual says 90 to 94 ? 12 valve is a 12 valve pretty much? except for the IP and LP and a few other goodies?. I never thought about it but one could check the Cat by welding a bung in front of it and testing for backpressure with a manometer. There was 3 different listing in the manual per application. Be cheaper than throwing a new exhaust in for test purposes.
Also if anyone needs any info I try to help. Torque specs etc bla,bla.
Also found it interesting they list IP`s from Stanadyne, Bosch and Nippondenso as canidates for the 12v.