I hadn't noticed it before until I got under the front of the car. One of the bolts had already been sheared off, the other one had the nut rounded by somebody trying to take it off but the joint wasn't blowing and I've been driving the car around for 3 years like this !
I hacksawed the bolt off at it's head but was left of the two bolts were absolutely seized solid on the CAT. I'm waiting on getting another CAT in the post I've bought on ebay complete with manifold and heat shield at a very reasonable price. I've bought 2 bolts with the 2 springs in good condition through Breakerlink.
The odd thing is though, the bolts on the old CAT look to be different widths so I'm wondering if there are CAT's with different fittings. I have a 2001 Y reg 998cc K11, I've bought a CAT taken from a 2002, 998 Tempest. I think the engine specs were all the same from 2000 until the K11's were discontinued in early 2003.
The K11 is the best little motor I've ever had for the money by the way.