28i noise between 4th and 5th

[Plasticmorph]

Hi, hoping someone can help. I bought a 28i auto yesterday and it’s my first convertible so I’m getting used to new noises etc.

I’ve just been out for a drive and noticed that shifting between 4th and 5th I can hear a quick ‘ssht’ kind of sound. I drove around at 30mph shifting between the two and it’s more noticeable on the upshift but present on both up and down.

Then I noticed that it doesn’t seem to happen at all in sport mode! Only in comfort mode.

Then I noticed that if I’m doing 30mph (ish) in manual mode in 5th gear and then switch from sport to comfort mode it makes the noise without changing gear.

So based on that, I’m thinking that I can cool my boots and my gearbox probably isn’t about to implode and it might be something to do with when the exhaust flap actuates?! Maybe it’s gear/drive mode specific.

Thoughts/experience?

(And yes I’ve searched… a lot!)

[Plasticmorph]

Incase anyone comes across this - it was the exhaust valve actuating.