Misfire -- 98 blazer

check compression, check valve clearance, check injector for properly working, check for vacuum leak around this cylinder.

What is your question ?

check spark plug gap and coil, also note any other abnormalities in engine performance, cylinder compression?

po300 is the code for multiple cylinders misfiring Probably tuneup time

#2 did what ? So it didn't drop rpm,then it
wasn't contributing much as the other were

You got a bad wire or module or whatever your car has

Check the injectors listen to them with a long screw driver
to your ear

For engine misfiring problem check the help links mentioned below. Click the link below to go through the troubleshooting procedure :---- Engine misses and truck jumps? Hard to down shift? Issue with high gear only? http://technoanswers.blogspot.in/2012/02/engine-miss-and-truck-jumps-hard-to.html

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Bad miss at idle?

http://technoanswers.blogspot.com/2012/01/bad-miss-at-idle.html

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While stop engine idles like cylinder missing?

http://schematicsdiagram.blogspot.com/2012/01/while-stop-engine-idles-like-cylinder.html

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Engine Misfire codes for car?

http://schematicsdiagram.blogspot.com/2011/12/engine-misfire-codes-on-chevrolet.html
Engine Misfire codes?

http://schematicsdiagram.blogspot.com/2011/12/engine-misfire-codes-on-chevrolet.html

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Misfire on cylinder 4?

http://schematicsdiagram.blogspot.com/2011/12/misfire-on-cylinder-4.html

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Oil on spark plugs and car misfires?

http://technoanswers.blogspot.in/2012/02/oil-on-spark-plugs-and-car-misfires.html

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This will help.

Thanks.

misfires can be caused by faulty ignition components, but they can also stem from other components. Such as faulty injectors, or improperly timed or unseated valves. Sounds like you have touched on all of your ignition suspects.
Are there any codes present other than P0304, P0305 and P0306? If so they should help guide you in the right direction. If not, You might want to make sure your valves are seating and if so, go ahead and swap an injector from a misfiring hole with a good one from a hole with no misfire. (like switch #2 and #4 injectors for example) if the misfire moves to cyl 2, you know the injector is at fault.

CYLINDER 4 MISFIRE...

check fuel for pressur and quantati to fuel rail posable fuel pump or regulator

If it is only doing this in overdrive lock up, tap the brake if it quits see a transmission man your torque converter might be bad