First tech post, new owner, first Caterham.. apologies now if not up to scratch with terms etc. Been lurking on the forum while I made up my mind on purchase, so many thanks for wealth of advice, information and experiences.. Bought a Roadsport 150 from S&C in Feb, absolutely love the car but didn't take long to start tinkering and fitted a decat pipe a few weeks back, largely for aesthetics but also for a little more noise, maybe power and to save the Cat. Looks better imho, bit better sound but can't say it's changed performance significantly. Maybe mid range but as said, I'm new.. Anyway, now the but.. After fitting, went out for a drive and the noise from the engine, I think induction (certianly not exhaust), was alarming. Thought a big end/s had gone, loud banging (like hammering wood), but only on hard acceleration and focused at 2800+ and with second resonance at around 4000/4500. So loud I refitted the Cat, went out again and noise gone although I can still hear a similar background tone, same revs but way quieter. Happy that the engine was ok, I've refitted the Cat (which now takes 10 mins), and the banging is back. I'm almost convinced it's induction and saw a description of "Induction hammer" which it kind of matches, but wondered if it was normal following a decat fit? Have to say the sound is impressive, so long as it's not damaging.. I'm kind of thinking the removal of the Cat has improved airflow through the TB's and attenuated their sound? Maybe running lean now? Bit out of my comfort zone on knowledge so could do with some advice or others experience please. Thanks Lawrence