If Im going to need a external cooler anyways it would not be a bad idea to do then! Yeah seems like the process of elimination is sometimes the only way to go, diagnostic on cars are not always that easy... I got the car tris time last year and it has only just started playing up over the last week or so, but I took it straight to my mechanic when it first happened. It has a full service history from the previous owner aswell, who was an older male who was very reluctant to even sell it, but financially had to. He never drove it real hard and was the only owner from new, so I know it has been looked after its whole life!! I do have a great reliable reputable mechanic so at least I know Im not going to get taken for a ride. And before you baulk at that last comment, he is well known in town, very good reputation and expecially known for his mods and for his work with XR6T's. Also my brother in law worked for him a few years back.