I don't believe HPI has ever produced any kind of "tuning guide" for their cars, except the instructions that come with the kits.
The 15FE as it comes stock, is a pig. The single needle carb really holds it back. You can buy one of the HPI hop-up kits for the motor (on their website) or just live with it until it's time to buy another motor.
It takes a minute or so to warm up from stone cold.