The DISA Valve is known to have some issues on these cars, so far mine is in working order. It works under vacuum and the valve is not loose or rattling. The gate door on the valve can come loose over time and get lodged in the intake manifold, so if yours is rattling change it asap! Or if you are boosted you can go with German Solutions DISA Valve repair kit. Their Direct link is here: DISA Valve Repair Kit. The press fit pin on the end can dislodge and fall out so be careful when taking out your DISA if it rattles.

When removing the DISA you notice that the flat OEM molded gasket is well, flat and not sealing properly, even worse if you have forced induction.

There have been some numbers thrown around like the water outlet gasket for a Ford V8 that fits in the DISA valve groove after removal of the OEM sealing gasket. that part number is Fel-Pro 35489 but that part does not fit correctly as it is way too thick!.

I found a suitable Viton and also Silicone gaskets from Oringsandmore.com for under $6.00 shipped.

You can get 10 Silicone O-rings for almost the same amount. They are this size: 2-1/4 x 2-7/16 x 3/32.

This is what happens with the fel-pro gasket:

Disa Installed with new Viton gasket:

Update 6/26/2012

A little while ago I did the G.A.S. DISA Valve upgrade and it is pretty straight forward. Anyone can tackle this job even if you have never worked on a car before. The directions sound intricate but doing the actual job is fast and easy.The GAS kit includes a wire to hold the rod, I didn’t use it as I didn’t think it was necessary.  The next thing is the use of the lag bolt, I just stuck a small screwdriver here:

If you think you can’t handle the job, well G.A.S. now has the DISA Valve gold which comes with a NEW Valve and the G.A.S. Repair kit already installed!