I have an 89 CRX HF with D15B6 engine. Had some problems with overheating. I believe caused by multiple reasons. The radiator cap was leaking which has been replaced. Radiator was also replaced recently. The cooling system was bleed to remove air. What I find odd is that the exhaust system blows stronger when idling then when increasing the rpms. The exhaust flow drops immediately when increasing the rpms. That would seem to indicate some kind of blockage however I took the entire exhaust system apart and the problem does not seem to the catalytic converter either. Also the gas mile has been fluctuating recently. The idle speed also fluctuates a little below 1000rpms. Could this be an ERG problem? Any other ideas?