need some advice

i have a misfire that only happens at idle. you can definately see the needle bounce a bit but runs good once i give it gas. its a 99 4.0 and it has new champion plugs, taylor 8.2mm wires, and new cap and rotor. could a weak ignition coil be causing this? or is this more of a bad fuel injector leaking gas. it also doesnt throw a check engine light and has no stored codes. its only at idle wether im in gear, neutral or park

Tps? Have you checked that?

How would I check the tps and would it not throw a check engine light if it was malfunctioning?