If you have tuning software, you can rewrite stuff as much as you want. You can even change tunes based on weather if you're so inclined. Unless you're having it dyno tuned by someone (or not doing it yourself), you're just going to get a cookie cutter tune anyway. Not very good for performance.

BTW, the Pacesetters have their own downpipe and get rid of the cat/ubend. You'll have to add the cat back in, but that's all.

A double roller isn't required for 105 springs, but if you go with it, you'll need the timing cover machined or go with the crude method of doubling gaskets. Don't forget all the new rocker bolts and so on.