Were you using 20% before?Its not a good idea to switch %s without some re-tune so I always stick with 20%. I understand the headache and smell issue of certain fuels. The Blue Thunder Fuel gives me a headache and my old p.o.s HPI MT ran like garbage on Blue Thunder, it could of been that it was a used motor but who knows. Blue Thunder also is so rancid it gives me a migrane headache almost like its pure poison. However, the Monster Fuel (purple) 20% I use now smells alot less rancid and never gives me a headache, plus my car runs great on it all the time.