Hi, my 95 WRX has developed a problem when starting, in that it fires up 1st time, and feels like it is only firing on 3 cylinders, then it will either cut out or if you apply the throttle it seems to cure itself and start to run on 4 again. if the engine cuts out it normally starts fine afterwards and runs on 4. It only does this from acold start, it's fine when it's warm. Any ideas? Is this a common problem?