Thanks for the quick reply. Beautiful car by the way.

Would you mind sharing the exact IPD plenum model you installed?
Did you do anything else to the car when the IPD plenum was installed (no matter how insignificant it may seem)?

Enjoy it in good health.

 

Thank you! Not sure about the exact model number but IPD has only one plenum specific to the 991 C/S. No, nothing else was done during installation.

 

This is exactly right. Welcome to the club.

 

Did you install it yourself?

And can I assume this is the one?
http://ipdplenums.com/products/plenu...-dfi-carrera-s

 

No, I did it at the dealership. Correct, that's the plenum..

 

Well, anyone else brave enough to give it a try?

If I could see one or two more confirmations I'd do it tomorrow.

 

I agree! But the website suggests a professional install. I wonder why? As I recall plenum installs in a Cayman, for instance, was a pretty straightforward bolt in. Is the 991 access the issue?

 

I have several thoughts. OT, I apologize.

• Has anyone ever done a before and after dyno on this item to prove the 15 horsepower increase?
• If it were really that easy (a modified plenum) to get another 15 horses, wouldn't Porsche have already done it?
• Is it just me, or does it look like the exact same part for the 3.4 and 3.8, with the same pictures, yet the 3.8 version is $50 more?
• It does look like a very nice part, and I don't mean to impune the manufacturer. It just brought up some questions in my little mind.

 

I would try this in a second if indeed it will help our stumbling issue. If a dealer installs it will it keep the factory warranty in place?

 

Most folks with the stumble are not looking for additional HP, but rather a smooth delivery of power under normal driving conditions.

There are Motorsport companies out there who perform ECU tunes and install similar components all day long, and are "unofficially sanctioned" by Porsche dealers. (I can think of two that are sponsors on this board).

However, this is a simple installation (depending on how handy you are).
As with everything else, it requires the bumper and air-filter housing removal.
The entire engine bay is a tight squeeze, so a bit of patience is required.

I for one would prefer a car that drives properly, as opposed to having a dreadful driving experience with a warranty.

Given that Porsche will not acknowledge the problem, what other options do we have?

 

I'm at the point where I'd gladly accept a 15 HP decrease if it completely cured the stumble.

 

^^^^^

Right there with you...

 

I wonder how this jives with the fact that stumble temporarily disappears after a re-flash or a battery disconnect? Are the two in any way related?

 

Georgefu did mention that his stumble always returned shortly after re-flashes and dealer fixes.
Exact same problem I've had on numerous occasions..

 

Curious as to how a hardware (plenum) swap can fix an apparent software issue (assuming the plenum swap doesn't require a re-flash).