When sending a pcm to pcm4less to have it reprogrammed, since it is getting rewritten, does it have to match your vehicle exactly? What I am getting at is: I want to have a tune done but I can't have my vehicle down for a week or more, I was thinking of getting a pcm from a Trailblazer at the local wrecking yard and sending it in to get reprogrammed, that way it would only be down for the 1/2 hour it takes to swap computers. I am sure there are serial numbers on these for a certain series of pcms, locally my research shows a couple of the same seriel #'s for the I6 4.2 as low as $40, found a 5.3ltr pcm for $50. Do I simply need any one pcm from a 5.3ltr truck or does it have to be a 2005 only, or a 2005 with AWD only, etc, etc? How much are they actually rewritting. Also, how many times can a computer be rewritten, is it like the memory on a flash drive that can be written over a 1,000 times or like some car computers where 3 times the limit?