True, It feels like engine rocking, as if rubber bushes have been removed and engine being directly fixed to metal or steering shaft.But I cannot think it as an issue related to fuel intake,because window is extremely narrow at 700-900 only. pre and post these rpm there are no issue (or may be I cannot feel them).It revs brilliantly til 5200 rpm. Idle with Ac on makes this vibration max. FASS techs thought it could be fan but it was not. Somebody suggested steering rod could be faulty-could it be ?