i did use the original NGK spark plugs #fr2b-d. as of the grade of lp i will have to check into that. i have never rebuilt a Nikki vaporizer but have rebuilt many Impco vaporizers and regulators. i removed the Nikki vaporizer and pulled the back plate and there is a lot of sludge in there so im wiping it out and cleaning it up. are these vaporizers really that difficult to rebuild? doesn't seem like there is to much to it