Mis-Fire Code: p0300 (warning, newbie knowledge) lol

Hello everyone, I have a couple of questions for my mis-fire. I have 1997 GT bone stock in and out. I recently bought this car September 2015 and have 232k miles. I bought it from a first owner. I'm new to the car scene so my knowledge is very broad, in other words I don't know much about my car as I should be, but I do got to start some where.

I remember when I was test driving the car, I tried doing a small pull 2nd-3rd gear. I've notice the car struggled pass 3k-4.5k rpm. I've drove the same model as mine (my friend's) I remember my friends sn95 was quite more powerful. I ask the previous owner why it struggled and he responded, "The cats are clogged". Don't ask, but once I bought it, I've been daily driving my car to work and completely ignored the problem like an idiot. It backfired when I took my car to a meet last week. My car can't even pass 80 mph even if I put my foot 100% on the pedal. That same day my check engine light came on. I've notice my car has been loosing power each time I drove it. The code is p0300 which is a misfire. With the lack of knowledge I have, I've look into my problem and basically put 8 new spark plugs. And my car still struggles going up a hill. My friend and I took each coil packs one by one while the car was on to see which one wasn't sparking. The tone of my car hasn't change when we took off 3 coil packs and the others did. So I thought it was the coil packs was the problem so I replaced them and nothing hasn't change. Even my distributor/spark plug wires are good. So I did a little more research and end up changing one of my fuel injection. Luckily I felt a little more power and was able to drive my car on the free way lol.

Since my fuel injection was bad, that's probably the reason why all 6 cats are bad. Right? Sorry for my lack of knowledge, a brotha needs help. So my next plan is to buy whole new cats or full exhaust set up. And if anyone have suggestions/advice or ideas feel free to comment below. Anything would help. If anyone wants me to take a picture or post a video of myself doing a 2nd-3rd gear pull I will be more happy to post it up, if it helps.

Here's my car. I just installed lowering springs, short shifter, cobra r, and mach 1 lip

 

Cleaned up the Maf today and idling is much better. I also checked my air filter fram and looks clean as well

 

It's not completely gone, but the idling is better, I'm not driving it once I completely fix the whole misfire problem

 

I live in California so it's definitely not going to pass. But I'm doing it anyways lmao. I just haven't search up what set up I want, willing to take suggestions

 

Hmm.. I should mind as well. I won't be driving this car anyways. What exhaust set up you're running?

 

Thanks bro! I feel very welcomed! Yeah, I'm definitely gonna listen to these guys

 

yeah, I probably have 2 cats, then save up for OEM for smog

 

So good news.. Instead of saving up $500-$1k to fix my problem. My good friend of mine is selling his 1996 Gt PI swapped 95k miles in whole for $700 lol. He recently wrecked the rear end and he has no insurance. So I'm buying the car for the engine and all the whole exhaust set, then will be parting out the wrecked one out. Once my taxes comes in, it will be mine lol. I'll post a couple of pictures in near future

 

Do you some how have a video by any chance? I would love to hear it