Q: Why does my engine sputter when accelerating on my 1992 Honda Accord.

I have a 1992 Honda Accord with a rebuilt transmission from reliable mechanics I've used for ten years. Long story short.. I have a slow oil leak & coolant/anti-freeze leak I check every other day & replace as necessary. I recently realized I left oil cap off on engine & drove about 40 miles round trip. (I didn't know I left off cap until I got home.) With lid off, while accelerating my engine began to sputter. It comes & goes & usually starts after about 5 minutes of being fired up & moving. It smoothed out as I accelerate higher. So, once I hit 40 mph for example, if I stop @ red light, it runs fairly smooth up to 40 mph, then starts to sputter when I try to surpass the highest speed I've previously reached. (41mph in this example). There are no crazy smells, just some burnt oil from where lid was off. My friend who works on cars for fun says I got air in the engine & eventually it will work itself out. Its been a week. What's your opinion? Should I rush to mechanic? Be patient?