You are wasting your money with an aftermarket DP unless you also address the intake side. You need a good CAI or SRI. I prefer the CAI approach. With this mod on the intake side you'll pick up a solid 15 whp or so. The restrictions in the stock airbox will prevent you getting enough flow to benefit from the aftermarket DP.
On the exhaust side, you need to decide whether to go catless. That's why I asked the question about whether you have to be sniffer tested.
DP install is not for someone without at least mid-level experience with exhaust system mods. There are threads on this. You need the right hand tools and know how to use them. You really need access to a lift to do it right. And you need know your way around the tight quarters involved in getting to and removing the nuts on the turbo exhaust outlet studs. You have work under the hood with the IC removed, and under the car. If you have doubts, let a good performance shop do this.
RP will replace the second cat and will help a little, but the real restriction is the restricive OEM DP and both cats.
The stock ECU will protect you with either boost cut or fuel cut if it senses danger. You do not need a tune to run a catted or catless DP/RP
Aftermarket CBE is a waste of money if you are expecting a performance gain unless and until you get your power north of 300 whp. Typically, you will see no gain with aftermarket CBE unless you go with a bigger turbo and a custom tune. Until you reach that level of mods and power, aftermarket CBE is just to change the sound. The stock CBE has excellent straight through design and will flow better than the turbo can pump air and exhaust.
The catless DP/RP was noticably louder and made the 60 mph drone worse. I fixed this by staying with the stock CBE and adding a third reso (3 inch) in the middle of the RP. It is now as quiet or more quiet than stock.
This combo really shines in the 60-110 mph range (third, fourth and fifth gear). I can consistently hit 60-100 mph in the range of 6.5-6.7 seconds, with quarter mile times at 13.5 (one 13.4) at 107-108, in good track conditions. This morning on the way to work, I got 6.54 seconds 60-100 mph by digital stopwatch, and 6.48 by accelerometer (GTech Pro RR).
Go to Road and Track's web site and check the posted times for 60-100 mph for other vehicles and you'll see how these mods compare. I use this for mod comparisons and tuning. By 60 mph you are hooked up and not dealing with all the variables in launch that can make data repeatability very difficult and frustrating in getting a good launch on a high hp fwd car, and less wear and tear on the drive train.
You will probably have a check engine light if you go catless. Just go to some place like Autozone and verify that the code number corresponds to running catless, and enjoy.
Finally, do not, I repeat, do not jump on board with the BOV crowd, especially avoid venting to atmosphere. That will cost you power. Unless you know your stock BPV is actually leaking, do the intake and exhaust mods first, and then, if you think you BPV is not holding boost in the higher gears, get an aftermarket BPV or an BOV that will run in full recirc and run it that way. Our MAF sensor needs recirc mode to send the proper air/fuel mixture signal to the ECU.
Fix your intake first, then go catless DP/RP. Just my opinion.
