You must tune the car if you run a catless dp and rp. Otherwise you will overboost by at least 2 psi and hit boost cut with nssty 21-22 psi boost spikes under certain conditions. Also, you must upgrade the high pressure fuel pump internals as the pump cannot keep up with the increased fuel demands and will drop pressure to unsafe levels. Looks like you already have the pump internals. You will want to verify that.

But, with catless dp/rp, internals, a CAI or SRI intake and even a conservative tune it pretty much maxes out the K04 on pump gas at just over 300 whp 300 torque. With an E tune as you plan you can probably get it up to 320-330 whp.

I've been running the catless TurboXS dp/rp for over eight years with mods below. Catless is also loud and droning even with stock CBE. I added a straight through reso in the rp section. That killed the drone with no detectable power loss.

The setup outflows the K04 on pump gas.

FWIW, @Carskick;, Speed Daddy does sell a shorty DP for our car; I just ebay'd one last week for about $85 shipped. If you haven't ordered the test pipe yet, that could be an option id you still want to try to pull off a catless DP/catted TP setup for fewer dollars.

I saw that, but I decided to just go TP and be done. Primary reason was cost of install and less risk of something going wrong. I may eventually change it, but that's the current plan.