When fitting the Lambda sensor you need to either grip the cat very securely or take it off to do it, otherwise you'll end up making your exhaust worse as it rotates with the force of trying to undo the Lambda sensor.
Alexisonfire - your nuts sir! I bet that goes like a bat out of hell now.
Much do you reckon your weighing in now 950?
It'll likely be tight, but that depends how long ago it was out and how it was refitted.
I could not undo mine while it was on the car, neither the first time removing it from the CAT, not the second time just a couple of months later from the decat.
If it was anything like mine, I wouldn't even bother without removing the cat first.
How has it been modified?
Removed 130kg which brings kerb down to 960kg, this is not taking into considering the new exhaust was half the weight of the original also.
The buckets and harnesses have to go back in which is around 22kg meaning 982kg kerb weight
Also bare in mind, average 6 point cage weighs 30-40kg, would be nice to get the car under 1 tonne with a roll cage.
Edit: oh and to say the car is loud inside is an understatementThis is with everything closed and the windows up