HI,,You will be fine if you stick with a 200 cell cat. system.
If you go with a 100 cell you might have a cell light,, Then you would have to try O2 extenders since you aren't going to get a tune..
Good Luck

you can bolt on an exhaust and the car will run without a reflash no problems.

but if you put on a system with no cats its likely your gonna see a CEL on the dash without a flash.

you will not take full advantage of the exhaust without the flash.
flash ups the boost level, increases timing, and leans the car out some.

I'm pretty sure you would want to add some fuel rather than lean it out.

OEM cars generally run fat, so id say 90% of tunes lean the afr's some and if you up the boost of course you want to increase the fuel trims to compensate.

Yes,, Agreed..

You stated flash ups the boost level. Raise the boost add fuel. So, I respectfully disagree.

It sounds like you're discussing two different things. He is saying the air/fuel ratio is set leaner. You are saying with more boost comes more fuel. You both can be correct and have both of these statements be true.

first part of this sentence says lean the afr's, second part says give it more fuel for more boost. increasing fuel trims to compensate for more boost would mean more fuel.

so technically its both!

When you flash a car you rewrite the target AFR's, boost targets, ignition targets. If you removed the limit on a stock tune it will hold the target afr the the stock flash is requesting(target) right up till the map sensor cant read and the O2's feed back is outside the +/- 25% trim. Talking about removing limits... Why do you think k16 and k24 flashes work so well? Yup Porsche/Bosch got it right and just limited the cars for the masses.

Add a good tune - it will WAKE up and you will love it. The "F-hose" that houses the diverter valves will split/fail eventually and will require replacement. That's a good time to upgrade the factory diverter valves that leak when old.

A good tune and exhaust makes a world of difference.
As dar as Tuning, oem target Afrs are pretty lean and the 997s even leaner (.85 lambda on boost) and that's how they make power with lower boost( among other things).

I saw dyno and AFR sheets on a few stock cars and they were on the rich side in the higher RPM range on full boost?? I thought and was told that's normal for safety reasons from Porsche?

996 more so then 997. But 997 is very lean.

The AFRs were in the high 10s on both 996 turbos

I can email you logs on did on my oem 997. Including te pic of the target afrs. :)