It takes a good 4-5 secs to start some times while other it’s instant. My gas mileage is horrible... I have changed fuel injectors, spark plugs, coil packs. Have also been putting seafoam into it. Also a very strong gas smell is coming from my exhaust. I don’t really know what else there is to fix this problem that has been ongoing for 3 weeks now...
It sounds like your engine is getting an alternate source of fuel somewhere, too much fuel pressure, or a mis-reporting sensor such as the coolant temperature, or mass air flow.
As @moab has kindly pointed out, your vehicle does not have a fuel pressure regulator on the injector rail as the slightly older models did, so that can be eliminated as suspect in your case.
A fuel pressure/leak down test should be performed, as well as a system scan of all sensor values, and modules for any other manufacturer specific module codes that might not show up on a generic OBDII scan. These tests should shed some light on where to look next.