Misfire?

I have a 1999 alero 2.4l It started shaking violently at a stoplight and died it has been hard to start and seems like it is still shaking after plugs, boots, coils ,crank shaft pos sen. changed it also sounds like there is something rolling around in the muffler.Compression seems good about 190 on all cyl.

I bought a scanner it pulls two codes both are po300 random cyl. misfire.

Could this be a cloged exaust?

Clogged exhaust is possible. Most likely at the CAT converter which will also cause the random misfires. You can get the exhaust system tested for excess back pressure.

Thanks i unbolted the exaust but it dident help so i replaced the coil housing again and it narrowed the misfire to cyl#1 and think i found the problem one of the new boots was damaged on install i hope to finish it tomarrow.