almost
It's the 3.2 manual, then red plod, then Transit, then silver merc then black merc.
That's the problem, after all this thread...I think I know that I'm just going to keep the 3.2 manual and not sell it on. You've driven the red plod, when the 3.2 manual is all up and going, you'll have to have a go...you'll know why it beats everything else 
This unmarked ex-plod of mine is the same - seems quite a bit quicker than the last one I had (ex-marked car in white) for some reason?? I know they always say that the police never tune the 3.2's engines, but...? :-/
As for your emissions issues (or should I rephrase that to your car's emission issues
) - not sure if it's any use or not, but I was getting the usual 0420/0430 codes on mine. Had a full new exhaust fitted (it was on its way out tbh), had the codes cleared, and they've never appeared since. Had it MOT'd round about xmas time, and the tester commented on the emissions that it was basically fresh air coming out given the readings. So, is your exhaust stuffed, or is it quite a bit mre complex than that??
Have a crawl underneath yours sometime and see if you can find a sticker on the diff. I checked the red 3.2 and it still had it on. That tells you if you've got an LSD or not. I know comparing non lsd and lsd auto's, the auto LSD's are much quicker. Not sure if the manuals would have any difference, but may be worth checking for the sticker.
If there's an 'S' in the botom left corner you've got an LSD.
I think unfortunately the emissions issue won't be cured by exhaust work. It missfires on the 1-3-5 bank after coming off enrichemnt, it's most likely a wiring issue to either the coil pack or lambda sensor. I can't claim any credit for finding that out, all thanks to James. So it may be new wiring in certain places.
I do keep looking at the pictures of your 3.2 manual in the gallery
