Decat Vibration

[s,one]

Just fitted my de-cat pipes and took the car out for a spin. Sounds much better now and pops and bangs like a good un. Question is I am left with a vibration at mid to high revs obviously as a result of my handywork.When I removed the cats there was a tie linking the two boxes together ,just a flat steel plate . I have re-used this plate and wonder if I have done the right thing any ideas where I should look first.

Cheers

Steve