doughnut gasket replacement?

What is your question?

I have put plugs and wires and a coil pack and a fuel filter on my '98 Ranger and it STILL wants to bog down and most often I can't get it up to about 3,000 RPM before it bogs. Can back pressure from a blown doughnut gasket(which the trucks does have a bad gasket there) cause this rough running? And, the timing of this poor running has been consistent and started about the same time).