Hi! I'm the proud but sore-faced new owner of a 2004 659cc Copen, I may be suing Daihatsu as I can't find any mention of 'permanent grin' as a possible side-effect of driving one. I bought her 8 days ago and as it was close to service mileage, located the nearest ex-Daihatsu place and had a full service done today, everything was fine except for a hole in the exhaust, for which they quoted me £427.28 for a genuine replacement from Daihatsu and informed me there were no aftermarket parts (except the ones I can see on Ebay for ~£150). I'm probably going to get a custom stainless steel exhaust made, mainly for the lifetime guarantee and I'm looking at places around Manchester now, however first I checked out what size to get and got a little education via google on how they work. Now I'm not really a car expert, I always just assumed bigger = more airflow = better, looking into it I read that too large an exhaust can reduce your exhaust velocity and actually lose power.. Looking at the table here How To Calculate Muffler Size and Exhaust Pipe Diameter - Exhaust Videos, I'm thinking 1.75" or 45mm would be fine right for a .659 Copen up to 108bhp, which is plenty of room for future tinkering without being TOO big. Anyone with actual experience and knowledge able to advise on that would be appreciated please! Future mods...as and when my budget allows. From reading various threads here, looks like a replacement manifold will be a big gain, as will either a sport cat (for emissions) or de-cat (if possible to replace the cat for the MOT ). I'm going to ask for quotes on a manifold and sport/de cat when I look for the exhaust, because I'm cynical and think the prospect of future work helps guarantee current work quality and might even drop the price on the exhaust a little, but I probably won't be able to get those for a while unless prices are much lower than my expectations. I like the idea of a sport cat to get a little more performance without MOT hassle, sounds like it's almost as good as a decat, but I've no idea yet on price differences though I'm expecting the cat to be a lot more expensive ofc, would it be worth it? For a de-cat pipe...I have this vague memory of seeing a youtube video of a guy swapping out his cat for a de-cat before a track run by undoing 2 clamps, took about 30s, can't find the clip again or anything like it so I'm not sure if that was custom or something you could buy, has anyone seen something like that? Looks like replacement standard turbos are scarce and pricy, so that might be a great place to go next, or at least plan for if/when mine dies. Prices on HKS turbos at a quick glance are £1500 (HKS - DX SPORTS TURBINE KIT) which sounds expensive, but prices on normal turbos are £1100 so...I've read ours are a sealed unit which can't be refurbished too, while an aftermarket replacement probably could, reducing future potential cost. Makes it seem a worthwhile investment? Wind Deflector - Mine actually has one branded with the name of a garage, it's just a piece of clear acrylic. There are sign and award makers who'll engrave and cut to size a piece of acrylic for £10-20 I've found online, or mirror-finished polished steel for £25 which might look pretty awesome, has anyone tried or seen any other materials used for them, or have other ideas on crafting one? Not a mod, but while I now have an ODBII cheapo bluetooth thing and torque which gives me lots of important figures, I find I have a slight problem with it. Even the values I vaguely understand the meaning off, I'm not sure what they should actually be, such as manifold pressure, boost (around 12psi?) ect, and I have no idea what an earth a 'fuel trim bank 2 sensor 2' is or why I should care! Anyone tell me what the main things to keep an eye on are and what ranges their values should be for a 660 turbo please?