Hi, new member with problems

Hi I've recently got an 06 rx8 off my brother as it is now struggling to run!

I tried to start it first off and just seemed to flood, after deflooding I was getting backfires.

I removed the plugs and they were gunked up so we cleaned them and they looked brand new. Put them in an a good jump battery connected and within a minute or so it fired and run quite well with only a very slight stutter about 6k.

After a small run it started to struggle so we stripped the coils and 3 were burnt so put 4 new ones on today and it won't start on the starter but will bump.

If you put it in deflooding mode you can hear it backfiring and sometimes comes back up to the airbox.

It started to smoke and run rough once it was running and a oily scented smoke was coming from the car and the catalytic was glowing really red!

The compression in the engine is good.

No mil light

Full service history at Mazda to 61k

Only done 66k

I've been going through the internet for about a week now and the only 2 possibilities I'm left with is blocked cat or engine failure!

Am I missing anything else?

Also if I just disconnect the cat would the engine run?

Any help would be greatly appreciated

Also any tips

Thanks

Dan