Darren_a6_3.0_tdi

Hello my names Darren, I'm new to the Audi scene and new to this forum im after some help!! i have a A6 3.0tdi ASB lemans Avant. i purchased the car last year and it had already had the rear box removed, I already had a plan of removing cats as heard they sounded awesome straight piped. so i purchased the darkside developments exhaust kit, once fitted i instantly started noticing blue smoke once warmed up and on idle. it varies how bad it is some days it don't smoke at all (or i don't notice it) other days it smokes badly but only notice it on idle/ i looked up on posts on internet and its pointing towards injectors my question is had anyone else had this issue? and is there a recommended place to send my injectors for tests or refurbishment