2003 trailblazer 5.3 p0300 code

hey folks I have a big problem with my 03 trailblazer. 5.3 ltr
It has the p0300 code and a hard missfire where it causes power lose and rough idle.
The missfire is noticable at all rpms.

Now I have already replaced the spark plugs and wires, the fuel pressure regulater and I cannot find any vacume leaks but it does when you hit the gas qwick give a sucking sound for a qwick sec but no other sounds like vacum.

but also if you listen on the passenger side in the wheel well when it is missing you can hear a clicking like a plug wire arcing but nothing can be seen.

the dealer of course tells me bring it in so they can charge me 1000.00 to find the problem.

My question is? is there a way to check the coil packs?? the auto stores do not list the test specs for them so what can I do??

please help if you can

You don't really see coil failures on these. It would be helpfull if you can get a scan tool and read the misfore counters to see excatly what cylinder(s) it is.