Don't be sniffin' gasoline, 'sbadforya.
Among other things, the benzene and hexane in gasoline will be metabolised to reactive species thatdamage DNA and protiens. In addition as others have pointed out, inhalant abuse can sensitize the heart to rushes of adrenaline and increase the risk of heart attack/sudden death, and since it's a solvent it causes all sorts of nonspecific damage to cell walls.
Stop solvent use immediately. No "weaning", no "titrating", stop putting gasoline in your body. Even chain smoking cigarettes is less destructive.
Seriously, knock it the fuck out. There are much better drugs you can do. Your body isn't going to go into gasoline withdrawals.
Nobody here is going to tell you it's OK to continue huffing gasoline, because it isn't. There is no constructive criticism to be given.
Stop damaging your body and start your recovery ASAP.