Hey having the same sort of issue, seems boggy, sluggish at low rpm, and shitty starting. I have changed the wires and plugs (waiting on coils) but could I be going in the wrong direction? I do have a little rough idle so I will be doing the coils anyways.

 

Can U tell me where exactly the ECU is located on the RX8?

 

Just get a compression test. Just ger 'er done! Its only $91 and if you need a new engine they'll refund the $91.