If you got another 100 hp without changing anything except run'n it, then there was/is something wrong.
LOL Maybe 'WAS' but I can assure you it's not 'IS'. And if it fixed itself, 'WAS' wasn't very bad.... It could be that I didn't get all the 'three year old' gas out the tank when I siphoned it. It runs like a top now. Over 300 miles yesterday without a miss.