Honda Prelude Engine Problem

My son owns a 97 honda prelude but the honda engine has the year 98 on it. It is a 4 cylinder engine for the honda sh. The 4th cylinder misfires. We had the engine head resurfaced and the 4th valve replaced as it was worn. We also put new piston rings in and spark plugs. The 4th cylinder continued to misfire. We then put in a rebuilt fuel injector, which I noticed has a "cross" opening on the end and the old one did not. We started the engine and then heard 2 small popping sounds and the engine continues to misfire. We have no clue as what to do next. Can you help us?Describe your problem.