Was driving my RX8 the other day and it just shut off completely on me. I turn it back on drive it, it had a very long start and you can tell that there was a significant loss of power and flashing CEL, was rattling really bad and I heard pops coming from the muffler. So I towed to the mechanic, replaced the coils and checked my plugs and wires were fine as I just replaced them 5 months ago. Anyone ever came across this?

 

Yes, many have had similar issues. Search some of the existing threads, you will find answers. Stalling and hot hard starts can indicate a failing engine but you should not jump to that conclusion as it could be a few things causing the issues you are having.

You can start here: Engine ---> Symptom Troubleshooting

http://foxed.ca/rx7manual/2003mazdar..._S01_0016.html

 

Yes, very common issue. The flashing CEL always means misfires, usually due to bad ignition components.
New ignition will usually help, but many times the type of issues you describe can also lead to catalytic converter damage.
Clogged or failing cats can also cause misfires eventually, even with new ignition.
If you have a cat, you need to get it checked.
Misfires kill cats, bad cats kill engines.