I have had the same generator for about 8 years.
It seems to have no issue putting out its rated output.
You can tell when it is on the upper end of its capacity there is a load on the engine, but it does not act like it is excessively laboring or on the verge of stalling.
One thing I will say, you may want to try a new spark plug.
I know it may sound silly, but I have had small engines that were doggy, and the spark plug looked fine, but a new one woke it right up.
Get an NGK B7ES.
I would be especially suspect it it still has its original made in China spark plug, they are known to sometimes be finicky.
Also if it has been sitting for some time and the gas in the tank is questionable, drain the tank and fill it with fresh gas. I try to find ethanol free gas for my small engines. Around here the only way to get ethanol free is go buy the 90 or 91 octane, so the cost is higher, but I have had no issues with cracking fuel lines or varnished or corroded carburetors since switching to ethanol free several years ago.
Edit: I just noticed you already posted you have ethanol free gas, so you are good to go on that!
