Noisy exhaust
 

Hi, I'm new to this forum and I've never posted to any forum - so please be gentle with me.

My Boxster 986 2.7, 2001 vintage, developed a deep burble which would come and go initially but now it is there most of the time.

Assuming that this was a case of a broken baffle in the silencer I have replaced the silencer as well as all pipes and clamps back to the catalytic converters. But the noise is still there and it is very difficult to work out quite where it is coming from.

I do wonder if it is the manifold or the gaskets, and that bothers me as I'd rather leave those bolts alone. But let me explain how the noise reveals itself and see if there are any ideas where I could look.

On cold start it is perfect, no noise. 500 yards down the road and the noise appears but most apparent at idle and low revs. Once I am accelerating it sounds good although I'm convinced the performance is down on what it used to be.

With the roof down the noise is less apparent - this may be because it is drowned out by wind noise but may also be a clue.

At last service there was an advisory about investigating an air leak - could this possibly be connected?

Also, I suspect one of the spark plug tubes needs replacing - or the O rings at least as I have a small oil leak from one plug.

Not much to go on I know, but before I start replacing more of the exhaust system I wondered if anyone had any ideas that I could chase down - I really don't want to touch those manifold bolts!

Many thanks

John