I would just pay the smaller upgrade fee to APR and run their IS20 stock downpipe tune (stage 3)...it's plenty, easy, and will be bullet-proof. I think you are hung up on the DP file thing - these DP tunes aren't any different from the stock DP tunes, they literally just turn off the CEL you get from the high-flow cat. With the R pipe, you don't have that issue. You aren't leaving any power on the table if you do the APR tune.