Cylinder misfiring 4 and 3?

I have a 1999 ford ranger 4.0. I have been getting a very intermittent misfire on cylinder 4 for a while now, it barely ever threw a code. On a long drive today it started shaking and occasionally jerking a lot. It threw a code and I got it tested it is saying goes 3 and 4 are misfiring now. Any suggestions on what this might be? It is running rough and it has to be taken to a shop now unless it is an easy fix. Thanks all

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