jon@work I know what you mean ... I must have a different bracket set up.
On my 3 door I've got a 90 degree bracket which bolts to the inner wing which I have taken off and blasted/painted ... where the MAP sensor bolts to it is unmolested and there is no sign of there ever being nuts welded on. Admittedly the hardware is obviously not standard ... it has socket head stainless bolts ... but to the best of my knowledge the bracket and bushes are.
I'm at work so I'm stuck for photos but I do have a couple of one of the best condition bushes.
Tev ... man I'm sorry if I've hijacked your post ... but I'm still interested to know if you have them (or seen them for that matter).