CEL is flashing, HELP!

Hello everybody, I own a 98 Rodeo 6cly. 4x4 automatic. Recently i been experiencing some weird idle and hard start, sometimes stalling. So i had the code read and they said my cylinder 3 is misfiring. So i went ahead and change the spark plugs since i haven't done so since i bought the vehicle. But it didn't help, still experiencing the same thing so i read on it some more and some said it might be the EGR needs cleaning. I went and got some carb cleaner and begin cleaning while i was cleaning I smell this weird odor coming out from the exhaust, is this normal? After cleaning it and clearing out the codes the vehicle runs fine for a good 10 minutes and the CEL pop back up and is flashing. When i accelerate, as the vehicle shift from 1st to 2nd it'll jerk almost like a thump and when it shifts back down from 2nd to 1st it'll jerk. It shake very hard and would stall most of the time when i come to a complete stop, but when i cleared the code it drives fine until the CEL pops out again and start flashing. I got the code read and here they are.....
p0121, p0300, p0171, p0174
Did i break anything while cleaning the EGR? any suggestion would greatly appreciate it. Thanks in advance.

It may very well be the IMG(intake manifold gasket). I'm pretty sure the 98's had issues with those as well. When I had my 99 it acted the same way when it went bad.

5 of the coils are the same and 1 is different The one by the brake master cyl is different.

the #1 cause for a mis-fire code is a leaking intake manifold gasket (I had mine replaced 2x within the first 75k miles).

Cost at a dealer to replace is 350-400 bucks.

The parts cost under 40 bucks.

click on my FAQ link below for more details on how to test for a leaking intake manifold gasket.

Thanks, im going to order the parts and replace it this weekend.

Guys i didn't change my IMG but i check my spark plug for oil and wetness and i found my 3rd and 5th cylinder were a little wet. so I put it back together and when i start my vehicle i see smoke coming out from the engine under the spark plug area and my CEL starts flashing. Could it be because i spray to much carb cleaner around the manifold area or does it mean my engine is shot. This is my first atemt at changing spark plugs. and i hear ticking sounds from my engine after i shut it off. Is this knocking sounds? Please help!

Just figure out why the engine was smoking:iceslolan. When i spray the brake cleaner around the manifold it didn't completely evaporate so when i start the car it just started smoking off the rest of the brake cleaner, lol.