I have a 04 rx8 231 hp with almost 100 000 km on it. It has a spots intake. Apart from that, stock engine whise.

As I took it out of its winter sleep I noticed that it's way down on power and it won't rev all the way to redline. But end of last season it was running great.

I have no check engine light or any fault codes, I have checked with a professional Delfi reader.

The cat was changed less than a year ago due to failed emissions test.
I have changed the ignition coils and leads (one coil was broken so it got a little bit better but it's still far from good).
The sparkplugs was changed less than a year ago, I have tried changing back to the old plugs and it makes no difference.
I have cleaned the MAF sensor, and wiped of the ess.

What more can I try, I am running out of ideas.

 

Did you give it fresh gas? Last winters is bad by now.
To diagnose further you'll need to hook up an OBD reader and look at fuel trim data ( give it a couple of drive cycles to learn the trims). If they're not near 0, it will give clues as to what might be happening.
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I have given it fresh gas.
If I remember correctly from when I had the obd reader connected there were 2 fuel trims, I think one of them was off by quiet a bit. I have to check again. Wat does it mean if it is off?

 

So on a warm idle, if the long term fuel trim is over about +7 you have a vacuum leak. If you see negative fuel trims that's very often a problem with the intake (many after market intakes cause more problems than benefit). Share what you find.

Note the car has to have had time to learn the trims, so a few drive cycles. Share what you find. Ideally, rpm, airflow g/sec, short term and longterm trim, and afr altogether on a warmed up idle.

 

Did you reset the NVRAM?

(20 brake pedal stomp?)