If your car has secondary cats with no sensors its a no-brainer as you will still pass emissions without them provided your main cats are hot when you do the test.

If you also replace the stock muffler with a more free flowing aftermarket unit like TopSpeed then what you get is faster throttle response and a nicer muffler tone without the drone.
Leaving the 2nd Cats in place with the TopSpeed mufflers only will result in an unacceptable drone.

It is still quiet when not punching the throttle and just cruising.

When you first go under a bridge and open your windows to hear the echos you will never want to leave that spot...it sounds incredible and will attract all the hotrodders attention immediately.

HP gains are unknown if any but the faster throttle will make your car leap off the line and potentially squawk rubber when you go into 2nd gear somewhat aggressively in an S model. You will be pushed back into the seat with some nice G's while accelerating hard in 2nd. :D

So do the mod and hang on to your Cajones (Edit Cojo's)!!!

It great to be "S'd"
http://goodlogo.com/images/logos/superman_logo_2940.gif

Your cajones are your drawers (as in a dresser or a desk)
Your cojo... are what you want to hang on to and protect ;)
Happy Porscheing,
Pedro

I don't want to be mean, just curious,
with test pipes I feel sportier sound, car revs faster and generally feels quicker.
What changing conditions are altered without secondary O2 sensors in? Sure it doesn't feel worse than stock.

Sorry guys, I didn't give a lot of attention till yesterday,
I saw my secondary CATs come with an 02 sensor at the begin of the CAT and then an 02 sensor at the end.
Is this normal for a 2003 year car? I thought these MY03 have one 02 sensor on primary CAT and one on secondary CAT.

I learned in another thread that Euro cars have O2 sensors in the rear cats. The Fabspeed pipes I bought have 2 bungs for sensors which I plugged but you will need.

Sorry, do I need to connect both of the sensors per pipe? cheers

If your car has them then you need them. It needs that feedback. Unplugging one will give CEL.

Me again! :eek:
Yesterday I was changing spark plugs and found that manifolds don't have any cats!
My car is MY 03 and manifolds look pretty standard.
I am surprised, shoulnd't I have two cats on them?
Cheers

I have the same set up on my car - euro spec car, apparently EU4 emissions - has 2 cats at the rear just before the muffler box.

Ok, that makes sense! so I am running with no cats then (the exhaust doesn't sound so loud as no cats at all, to me, still similar to stock at low rpm, then high ad 4K rpm of course).
I will try to put 2x O2 sensors on cat bypass and 2x O2 sensors out somewhere to pick clean air, that should fool ECU and remove CEL I believe.
Cheers,
Ser

I don't know what your emissions test is like in Gibralter but no cats in UK would surely fail. As you have found out Euro cars only have 2 cats, what everybody else here calls secondary cats. I have just fitted 100 cell sports cats and had to space out the rear lambdas in an attempt to stop the CEL triggering. I guess you will need something similar.