my exhaust is blowing near the cat i get rid of the cat and run my exhaust without one???
Yes, but if you have to get emissions checked, you're screwed.
That is the question... do you have required emission tests? If not, you'll get a little better mpg w/o the cat. If you have the tests, find out what the rules are for your car. In the US, the first "green diesel's" were IDI with a cat. The emission standards of the day (1986 ?) did not require the cat. And in Michigan when they did have testing in the Detroit area, if you failed a test on an older car, you could get the mechanic to sign-off saying it was too costly to repair, and you had your pass on the test anyway.