I went with a pci harness, but pulled mine to go back to an Olds motor on the current project, so am talking research I have done, but no real first hand experience. I would take the time to at least unwrap the harness and eliminate the unnecessary wired down to the connector, and seal them off from there. That said, it is just a step or two farther to pull the pin. Fewer chances for unexpected glitches, and a cleaner install. Skid factory has a couple vids on Youtube covering the process of merging harnesses, which I think I will do when I put the LQ4 in the Malibu I picked up. There are a few other vids on the university of Youtube that are worth watching, and LT1swap.com has a shat ton of useful info as well.