Shillidincha

Thanks guys, the guy I bought it from said he maintained it very well and it came out of its MOT the day I collected it and it passed with minor advisories ( nothing engine related). Yes it does, normally motorway - or highway ( I'm guessing some of you guys are American) speeds, I can only best describe it as like a cough, the car still drives but its really irritating! Well thanks a lot guys for your help so far, I'll get changing the suggested items and see if that makes a difference (hopefully it does)!!

I've just bought a 2001 legacy gx 2.5 automatic about 3 weeks ago or so, had some over heating issues, but a thermostat change luckily fixed it, but I'm noticing when I'm driving on the motorway about 60 mph + I can notice that the car seems to be almost misfiring. It comes and goes and only happens when I hold the throttle steady. The cars got 138000 miles on it, hopefully someone on here can advise me on what they think it may be, I'm hoping someone is going to say spark plugs / wiring loom / or get a terra clean treatment - something relatively easy to sort and NOT head gasket (I know a lot of subarus go at about 150k) / the engines knackared!! Looking forward to any advice / replies