[68gmsee]

Can you see the exhaust at cruising speeds? I find it hard to determine a slight leak when driving down the road unless it's really bad or have someone drive behind me that is familiar with the darker/grayish color of fuel, bluish color of oil or white to light gray color of coolant. Sometimes these colors are very subtle and hard to determine but the best way to know for sure is to have a shop with engine exhaust analyzer check it for you. The better ones can analyze even minute amounts exhaust that one can't see at idle.

One other comment. A compression test may or may not determine a problem with valve guides and/or head gasket unless the gasket leak is severe. A leak down test is better in this case.