ok i have an 05 in the winter it runs like a champ but when the weather gets hot the idle drops and almost stalls out i have a huge power loss, ive changed the oil, plugs, wires, and coils, ive done the air box mod to alow more air flow, and ive tried the throttle body radiator hose by pass so far no luck im running out of ideas to fix this without chalking it up to a compression issue which im hoping its not. like i said it runs fine in colder weather i only have this issue when its hot out. anyone have other ideas i can try?

 

Does it make a change in sound when its losing power?

 

check your CAT.
Are you getting a CEL?

 

Its not the cat or the issues would be the same in both the Summer and Winter. I hate to say it but it sounds like a compression issue to me. I used to have the same issues with my last engine.

 

im not getting any cels, and when im on the gas and hit about 5000 rpm it makes a rattling noise which sounds like it is coming from about where the cat is.

 

Mine also makes a noise near the rear of the cat, except I bought a newer high-flow cat. I just assumed i didnt tighten the bolts all the way 100%. I too have power loss and a disturbing rattle above 4500, but not below. The dealership said they though my problem was related to the exhaust, but I didnt think much of it...

 

We had the same issue and turned out being the compression issue...The engine and catalytic were replaced. Luckily the car was still under warranty and Mazda picked up the tab...

Good luck!
Sue