I have a manual CRX with a Type R engine. When I go about 80 in 5th I hear a loud clunk and I lose power also I think the RPM are a bit high for this speed about 5k. Now I try not to push it so hard to avoid this, I thought at first my clutch may be slipping but the symptoms don't add up also when I get up to those speeds I smell as if the oil is burning. I had the oil replaced with full syn and transmission flushed two days ago and today I heard the same noise at about 75/4.5 RPM and quickly got off the gas and continued at about 65-70/4.2 RPM with no problems and no smell. Can anyone help me to diagnose what the problem might be?

Thanks- Jay