My car has just started to make a whistling noise while on moderate to high boost. I had a look this weekend at both sides of the intercooler and both seem to be clamped down pretty well.
Only thing I have recently changed is installed a new 2XS BPV. I changed the spring on that from blue to yellow and this had no obvious effect. I did notice inside one of the rubber rings was not properly seated and fixed that up.
I also got some extra tubing to connect the T piece to the boost sensor part (no idea of proper name for this) on the BPV because I was worried I wasn't clamping on properly.
To describe the noise its a high pitch noise which at first sounded a bit like a superchargers whine. Got more high pitch as boost increased.
Anyone had any experience of this or suggest places I should look? Only places I can think are that the O ring on the bottom of the BPV isn't seated correctly (was a hard bastard to get into place, had to use a bit of water to get it to stay put and even then lost it for about 10minutes at one point) or that my car is sucking in through the Meth/H20 system, which I believe shouldnt happen and hasn't up until now.