I am planning to put a 3hp Briggs on a db30 doodlebug and I don't want to rev its heads off; Are there upgrade valve springs? And studz racing hasn't gone back in stock for a while for the 3-5hp Briggs to Mikuni carb intake. If that is the only source, what other intakes work where the carb isn't tilted or close to the stock exhaust? or what other carbs work in general?