The exhaust manifolds crack as mentioned, almost every 20VT will suffer from this at some stage. Some have been through several manifolds. It's not a big performance problem, but sounds pretty horrible when the engine is cold (the crack tends to seal up when the manifold gets up to working temperature). New manifolds are available (£240+vat) but cracked ones last well if properly welded (i.e. not MIGed!).
Turbos can fail, just as they can with every other turbocharged car. The Coupe is nothing special here, if it's been looked after with regular oil changes, driven gently when cold and allowed to cool down after a thrash before switching the engine off there is no reason for them to fail prematurely. Re-conditioned turbos are available from around £300, and they aren't that bad a job to fit.
People will like to frighten you about the cam belt, suggesting that the engine has to be removed to change it, which is complete rubbish. It is however, very, very tight against the inner wing, so the engine mounts have to be removed on one side and the engine shifted around. This is labour intensive, so belt changes aren't especially cheap if you don't fancy DIYing it (and you need the camshaft locking tools). IIRC the specialists charge around £350-£400 for the job. I did it in my driveway for just over £110 including the locking tools, but YMMV.
It's very important the auxiliary belts are changed at the correct interval, if they snap it's very possible for them to get wrapped around the back of the crank pulley (poor design IMO), and cause timing belt failure.
Front wishbones are very much consumable items, the torque of the 20VT and the weight of the engine give them a hard time. Fortunately the parts are pretty reasonably priced (~£40 each for OEM items, as low as £15 for pattern parts but they don't last as long). On the subject of suspension, the rear radius arm bearings can wear at high mileages, you'd need to jack up the car to feel any slop in the bearings, but if the car is showing noticeable negative camber at the rear then they are probably worn. Repair kits available at around £25 a side.
I would suggest you avoid cars that have had the boost increased over standard. Many people put in a generic chip upgrade (GTEC1 or GTEC2) and a PRV to stabilise the boost control and then never bother getting the fuelling checked. Many engines have died like this (including mine before I owned it). If it's running stock boost (~1 Bar) and has a PRV fitted, this isn't such a bad thing as the stock electronic boost control can be a bit ropey.
Oil pressure is a continual concern to 20VT owners for some reason, they get paranoid about it. As long as the engine will hold more than about 1.5 bar at idle with the engine fully hot, there shouldn't be a problem and the pressure should hit 3 bar (end of the gauage) if you increase the RPM to 2000 or so. Note that some of the engines tend to use rather a lot of oil, and almost every week there is a tale of woe on the forum after someone has killed another engine by letting the oil drop too far.
Other possible engine related faults are pretty much the same as other marques, e.g. Mass air meter faults, the occasional coil pack fault, stuck thermostats, rotting radiators etc. Engine mounts are a favourite on high mileage examples, listen for any clunking pulling away or when changing gear (though this can also be caused by loose wishbone mountings).
The big Brembo brakes at the front have a healthy appetite for disks and pads if you use the cars performance regularly, and some pads have a tendancy to squeal quite badly. Shims are available to fix this, and the disks and pads are used on several other cars so they are not stupidly expensive.
Headlamps are crap as standard, the dipped beams use projectors with standard halogen bulbs, so the amount of light that actually makes it out of the lens is pitiful. Upgraded halogens help, but a HID conversion is the way to go for half decent lights. Main beam is fine with just upgraded halogens IME.
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