If an ABS or ESC system has been intentionally rendered inoperative,the whole system must be removed. However, this does not apply to sensor rings or other ABS components which are an integral part of another component e.g. brake disc or driveshaft.
afik this is still current, not sure if it will change this year but not read anything that mentions it.
It must have been one of the drafts in the last round then, but there was definitely discussion of not passing cars with ABS removed where it was originally fitted, i.e. a clio cup is fine, but a 172 with ABS removed wouldnt be. As you say though, it's not in the current manual.
Interestingly in the draft manual for this year it says:
"It is not permissible to remove
or disable the ABS from a vehicle
first used on or after 1 January 2010"
Which I guess means they realised the records available werent actually good enough to determine what cars had or did not have ABS prior to that date.
Removing a cat from a turbo car can see a lot bigger gains than 5bhp!
Removing just the cat, in new condition? Without an exhaust, map, downpipe etc?
The point is that the "decat" was a max power era mod, and the gains were wildly over hyped. Even now you see people with trackday 172s wearing their decat pipe or hooky MOT tester like a badge of honour and its all b****cks, just leave it fitted and ignore.
On a big power turbo car, fair enough, but TBH, with most turbo cars, you'll be buying an exhaust and a map anyway and most likely a larger downpipe, so just upgrade the CAT as well.
Totally agree that the wording is very open ended, it was however snuck in at the very last minute after a LOT of lobbying by the rally world because without it, the new rules would effectively have made all that you describe illegal.
It's annoying that you can't argue black and white what is and isnt acceptable, however I'm still of the opinion that if it stops folk MOTing otherwise standard "track cars" with defective ABS, airbags etc then it's a positive thing, they just need to sort out the exemptions.