Would using higher octane gas give me anymore HP in my 4cyl engine? Aslo would I have to worry about stressing the engine too much?

no it won't give you more HP , just cost you more money at the pump , if your talking about a tracker it was made to run on the low stuff , like around 85 octane

Absolutely correct! If the engine isn't pinging during acceleration, using premium gas is a waste of money. Of interest....30 years ago 91 octain was Regular Gasoline!