Octavia Misfire

I have got a 2007 Octavia 2.0 tfsi that has done 95k completely standard. Cold start the engine has a constant misfire. Once the engine has warmed up it will run fine for a few minutes, and then starts to misfire and cycles between ok and misfiring. I am getting a fault code of misfire number 2 cylinder. I have changed all the coils and plugs and swamped number 1 and 2 plugs and coils to rule out a bad new part. I have taken the inlet manifold of and cleaned all the inlet valves. Could this be a faulty injector or am I missing something obvious? I am not keen to repeat the hell of taking the manifold off again!