If there is no record found of the agreement made last year allowing you to use HOA funds, for gas reimbursement in lieu of salary as compensation for your time, I would contact the former HOA board members. You should have them write out statements, signed and notarized, verifying the agreement made. Present these signed statements to the current board.
It wouldn't hurt to have an accounting of all HOA funds used as reimbursement, and all of the corresponding gas receipts.
If the HOA board continues to accuse you of the misuse of funds, even with the evidence presented, contact an attorney.