Depends mate, does yours have a DPF and also if not which cat are you planning on decatting? There is a precat after the turbo which a decat will give a little performance gain and also better spool up of turbo then there is the 2nd cat, also there is a middle and rear silencer but i think thats slightly different for cars with a DPF.
I dont think an EML will come in if your just doing a decat but i think a DPF removal with just a pipe and no map will bring it up
Unless your friendly with your mot tester
I decated my 06 mjet which has been mapped to 195hp and It lost torque. It made the turbo spool up quicker but you couldn't feel the grunt as before so i put the cat back on, no point decatting unless you hybrid the turbo.