Whenever the rpms get up around 2000, the engine or something starts whirring(or somethin like that) for a few seconds and stops around 4k rpms. It sounds like a there's a crack in the air filter housing box, or it's not completely shut or something. Any idea what's makin that noise? And there's a slight knocking when I start movin and keep it at low rpms. What gives? I got a 2000 1500 5.2L