Check engine light will come on after start up and returns to normal idle. Will go off if I have to put it in a high load or rpm situation. Like passing gear. But when Roma return to normal driving rpm light returns. I have replaced tps ect, and cleaned egr valve. Checked all vacuum hoses,y question is could a very, very small intake gasket leak cause this kinda situation? When idling engine not producing enough vaccum to satisfy emission controls, but under higher Rpms vacuum is satisfying controls? I cannot sense a intake leak or find one . What do you Suggest?