So, the time has come to get rid of the poxxy stock exhaust on my VDJ79 landcruiser. I was looking at buying the manta 3" twin exit system (with cat), as they sound dead sexy and I've heard good things. I also popped into the local exhaust shop who have had quite a few VDJs come through, and they quoted me a bit less to fabricate and fit an identical system than to buy the Manta system. Now I had the dangerous idea, why not see what they'll charge to do the twin exit system in 4" instead? For those who have experiece, how much louder is a 4" than a 3"? I'm hoping that a 4" with give a deeper note, but I'd still like a system that's not obnoxiousy loud. Secondly, do you think a 4" is worth it for an extra hundred bucks or so with a high flow cat, or does the cat make the extra inch redundant. Cheers.