a long time ago i rolled by buddies runner (22re) when it rolled the motor moved enough to crack the rubber tube that hooks right to the intake, it did vary similar things to what you stated. 4lo or going up a hit is the worse. basically the crack was at the bottom of the rubber tube and opened up once there was torque on the motor. (like going up hill or 4low). but since it was pretty much closed when there was no pressure on anything driving a flat road or just idling was fine. take it off and check it out.. may be your problem.
