L5P Test Ecm

We run into "funky" tunes every now and then. Codes blocked, weird fueling and just people not knowing what they are doing. On older ecms I can review the tune and sometimes pick out an issue or see relevant codes blocked but with the L5P's being write only I'm blind. I'm trying to set up a test ecm. If I unlock a spare ecm and do a vats off tune would it be able to start and run a truck with a vin mismatch? Paying 400 to change the vin every time we want to use it isn't economical but doing it one time would be worthwhile. Or am I best off programming with SPS through GM when we need to test with it. Any advice is welcome.

Best to use SPS