Loss of Power is Driving Me Insane
 

I have a 07 RX-8 AT with 92k miles. I bought it used from a local dealer and when I bought it, it ran fine for the first month or so. Just recently I noticed the loss of power. I could put my foot to the floor and it would stay in 3rd gear and never go over 4k rpm, but when I let off the pedal it would shift through the gears. It through a CEL and the code read P0411 and P0410. I had it diagnosed at my nearest Mazda Dealer and they said that the VDI Solenoid Valve was going and to replace that. I replaced that with no improvements to the performance. I called them back and they said it was the airbox that needed replacing. By this time whenever it would get close to 4.5k rpm the tach would jump up and down from 3k to 4.5k. I eventually replaced the airbox with an AEM CAI. It had a little bit of improvement but still no power. Now whenever I get to 4.5k rpm it sounds like a valve is suddenly opening up and it sounds really loud. I also cleaned the throttle body and that didn't help. Anyone got any ideas?? My biggest fear is that the dealer is sending me on a wild goose chase hoping that I run it out of warranty so they can slap me with a huge bill.

P0410 - AIR system problem
P0411 - Secondary air injection system incorrect flow detected

Coupled to the "sounds like a valve suddenly opening" - it appears your problems are likely associated with a leak in the intake system?

Perhaps this could be of use to you:

i had a similar issue when i first switched back to oem airbox in my rx8. The engine would idle rough and would not rev over 4k but would go through the gears fine if i kept it below 4k. It ended up being a loose clamp on the intake hose to the throttle body. Make sure are your hose clamps are tight and all vacuum lines are properly routed

I made sure its all tight. Mechanic said it might be the catalytic converter clogged up.

If your cat is clogged then you'll likely want to check your whole ignition (coil, plugs, and wires).
Running around with a clogged cat can quickly lead to needing a replacement motor.