I just installed a THDP and no fitment problem fits PERFECT...no hits. But...always a but, I used a torque strap to keep the motor from rocking due to motor mounts that are tired. I knew if the stock DP pipe hit the upper control arm the THDP would also so, I put the strap on the keep the motor from rocking and hitting.
Now as far as power increase ....awesome, it is a different car...you can just tell it breathes better and I get better mileage and it is louder.
ATR 303 not sure of but the THDP was a piece of cake.
USE PB BLASTER (not WD40) ON THE RUSTED BOLTS, etc.