deleting one cat good enough or delete two ? (downpipe)

I have already made a thread but this is based on another question, so I hope I can get some help with this.

My main goal is to go near full BPU. I already have Blitz NUR SPEC R catback exhaust, Blitz midpipe, Blitz intercooler with 3" piping, Blitz TWIN INTAKE, and more...

My next mod I want to focus on is the downpipe. I am having a difficult time finding a FULL JDM downpipe for a decent price so I am looking at alternatives.

I found this item which is a 1st cat delete. If I get a full downpipe which deletes both cats this means I would need a 2" restrictor ring not to overboost? If I just have 1st cat delete and leave the 2nd cat in then I don't need any restrictor.

So will I make the same power with 1st cat delete apposed to full cat delete with 2" restrictor?

http://img534.imageshack.us/img534/3462/supra216953753569.jpg

the size is 76mm of this 1st cat delete pipe... the seller also claims its good for 30hp increase. Most of the full downpipes are rated at around 30hp increase as well so this is another reason I ask my question.

I may be wrong but I dont think you get 30bhp from removing a cat, the extra potential bhp can be released by taking away the restriction but the hp comes from increased boost. Alot of people keep 1 cat in and its best to keep the 2nd to take away the heat close to the engine that you would get from the first cat. I removed the second cat and left the first to start with and I still needed a restrictor ring as the car still produced to much boost with the restriction gone. Best bet if your not concerned about emissions is to double decat and pop a restrictor ring to hold back boost either to 1.1-1.2bar and be done with it or hold boost back to 1bar or so and use a boost controller to raise from there. Just removing the first cat with a good cat back exhaust is good enough though but you will more than likely still need to play with a restrictor ring