911_RS

Thinking of getting the full system for my 991RS… GMG headers with 200cell cats + side delete mufflers + rear center muffler delete with 4" tips. Will it increase power? like 20hp? CEL problems? I know the sound will be amazing though!

Metzeger

Yes go for a GMG. I wait mine bypass James and his team help you in our choice Like me

911_RS

Nice! You won't get the GMG headers?

911_RS

Or any other full exhaust for the 991RS? Saw some GT3s with IPE full exhaust… What about Akrapovic?

Metzeger

No Just for the moment the bypass Exhaust

Metzeger

Akrapovic is too expensive... And IPE i'm not A big fan and you loose torque... GMG have the knowledge of Porsche sport cars and motorsport expériences

911_RS

You got that right!

karimgt3

I was thinking the same for mine!

Don't mean to hijack your thread, but has anyone thought of headers only? Catless? while keeping all the rest as is.. Is it better for maintaining back pressure?

Money2536

I'm sure James will chime in on this one, but I would guess 20hp a bit too optimistic. I would guess you'll gain some torque in the midrange, but who knows with 4.0. All there is to be had may already be there. I'd be inclined to give the Center bypass a try by itself. Then you could add headers later after making sure you don't have any engine issues. I think service departments will be a lot more forgiving on a bypass versus a full exhaust.

tripleblack

I had a close look at the exhaust system last week and would be very surprised if there's a hidden 20hp there (cat removal/changes and tunes excluded). The headers, in particular, look very good.

MM3.9GT3

Before you purchase anything, GMG or any other brand, ask for their warranty on the cats when the car is used at the track.

MM3.9GT3

Porsche goes from a 3.8 to a 4.0 with a bunch of other changes, and HP goes up by 25. So, your skepticism is warranted about the extra 20 HP.

911_RS

You have a point here... Or at least some hp gains at the low and mid range because of the headers and 200cell cats?

911_RS

I'm leaning towards GMG, I like their design and they have big involvements in the motorsport industry. Let's wait for James' reply on this matter. 😊

911_RS

I like a set of cat delete headers too! But I'm gonna wait for the GIAC tune first, so I won't get CEL problems 😊