Ok, I have an S5 N/A RX7, stock exhaust setup. The last few days I have noticed a drop in power, and the damn thing got louder. I drive my car a lot everyday so I can really feel it when something changes. I look under there today and I see a little pipe coming out of the cat and it has seperated from the cat. Ok my first thought is this **** should be connected. Anyway I am pretty sure this is the problem, but what are my options for fixing it? I don't have a welder and money is tight.

 

The pipe from the exhaust manifold to the cats probably came loose, it happened to me twice with the n/a stock exhaust, raise the car and check it out. you'll need a new gasket and stuff. When mine came apart it broke the damn nuts off the bolts.

 

The small tube you are talking about is the split air pipe. It supplies fresh air to the cat via the air pump so it can burn the fuel off and not overheat. It is louder because it is allowing air to bypass the cat and mufflers and just come straight out. Try and see if it seperated at the junction, and you might just need a new gasket and bolts. It it broke off, like I've seen with many cars, you will need to take it to a shop to have it welded back on. It will quiet the car down and you will regain your power, because all that the broken tube is doing is causing a large exhaust leak.

 

also on an s4 i believe the 5th and 6th ports are actuated off of the airpump/emissions equipment, get someone to clarify this before you take my advice.