De-Cat pipe, will I need retune if keeping stock silencer?

[duncanpage]

Hi all

Wonder if anyone can help me.

I've just ordered a de-cat pipe for my zx6r 9f. Basically I want to keep the stock silencer for now (partly because I don't want to attract too much attention to the bike when parked up and also because the girlfriend isn't happy with me spending money on the bike when I am supposed to save for a mortgage! )
So I just wanted to know will I get a marginal increase in power/fuel economy with just the de-cat pipe or will I have to get a power commander?

If I get the power commander will I be able to use a pre-programmed setting or will it need to be set up on a rolling road?

Any help would be greatly appreciated