I don't know when your Haulster was mfr'd, but be vary careful of compatibility of the solvents in the new cleaners/additives with the components in the older injectors. A friend had to have all of his injectors replaced in an older Nissan Maxima. All he could point to was the injector cleaner he used at a fillup.

Larsol

Interesting.... made in 2000

Wheelhorse: I would recommend Lucas Top end Lubricant fuel Injector Cleaner . It has proven quite useful within carb / injector cleaning and valve / piston carbon reduction within Snowmobile , Snowblower , Chainsaw and lawnmower usages . It combines a solvent and lubricity factor which increases overall engine performance . $4.00 bucks for 6 oz bottle , normally I use 2 ounces per 2 Gal container x 2 for 5 Gal . On stubborn fuel restriction issues 2 ounces to fresh fuel tank for small engine projects .