When i worked at Piper and we did this development, we found that a 2.5" bore downpipe was the best option for the K03/K03s turbos. They can comfortably handle up to and beyond what the turbo is capable of flowing (260bhp). We found that going larger caused a great deal of turbulance in the downpipe and the flow was reduced up to around 4000rpm, and after that was only the same as the 2.75" and 3.0" versions we also tested.

With the cats, we decided upon a 200CPSI as the flow difference between 100 and 200 was neglegable. The 100 did flow better, but because it has less coated surface area they do not last as long. If you plan of keeping the car a while, i would advise a 200CPSI version. If you either do few miles, or do not plan on keeping the car too long then a 100CPSI will be fine.

I cannot say if either will cause a problem with the MIL light as my car was allready mapped for a sports cat when we did the testing.

I hope that gives you a little insight into the various options

Kind Regards

Garry

Totally agree here Garry.

I have had cell 100 BlueFlame and cell 200 Blueflame on mine, both 2.5" and good downpipes / cats. I went with a cell 200 after i thought the cell 100 was failing mot but turned out to be a dodgy postal remap overfuelling. I intended to keep the car a while and was made aware that the cell 100 life span is quite a bit less that of the cell 200

The new Blueflame cell 200 are also made better than the older version.

So that sold me. What with the REVO 2 remap the sound of the cell 200 makes the rest of the system sound sweet.

ive got the jetex 200cel cat, coupled upto a haywards and scott sytem, flies through its mot even when cold.

made a heap of difference compared to the standard system as well

Cheers for that Rob, didn't know the standard downpipe was so skinny! Don't suppose you could check the diameter of your old one after you whip it off. Just interested to know.

Will do - I plan to keep the old one just in case.

...and decat 2.5inch, lots of noise, popping and banging, cell light on, improvement in mpg and pickup noticeable, cheap as chips on various sites, wont pass mot

Sounds interesting - I'm getting the second O2 sensor mapped out so will get no CEL - popping and banging will be fun!!