Get under and look for signs of leaks. Dripping water on cold-start, cracks on joints/pipes, loose fasteners, or sooting
- You can also spray some soapy water, but you have to do it close to cold-start or else it will vaporize instantly and won't give you any indication (also thermal shock not good for pipes)
You have a flex fuel kit, so it could be something related to your fuel, fuel map / response
Delayed throttle response could also mean MAF, dirty throttle body, or bugged idle learn