i have a 1997 toyota 4runner and the engine is backfiring on 1997 Toyota 4Runner

changed the fuel filter and sparkplugs and wires changed the front 02 sensor as well im out od ideas? any advice helps thanks

Asked by for the 1997 Toyota 4Runner
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is it back firing thru intake or exhaust?
yes its back firing through the exhaust, but intermittent it also has power loss and is hard on gas.... i looked under the hood and it calls for dual prong sparkplugs i used the single prong ones.... it doesnt run bad all the time thou just on occasion im planning a trip to the beach and want to get it fixed before we leave thanks for any advice
start with the proper plugs