The X belongs to my wife and since we bought it(30,000 mi then - 60,000mi now) we noticed that the exhaust stinks.We have had it to the dealer many times and no one can tell us what it is. It to me smells kinda like the catalytic converter is bad but no loss in performance or service engine light. Also we only use 93 octane fuel in the car but have tried other brands and grades to see if anything changed. For most people the exhaust smelling would not be a problem but we are fans of driving with the windows down and at every stop light that stink blows right in the windows if the wind is right. Any ideas what this could be and how I could fix it. Thanks

Have you checked to see if there's a leak after the muffler that might filter up into the cab?

If the truck is not obviously loud, I'd start with the simple (look for a leak) and then go into the less simple and see if there's contact somewhere that's causing the exhaust to possibly heat or come in contact with some of the shielding or body panels as that could cause road grime to be baked off on a fairly consistent basis - which I can attest to being potentially rank as there have been plenty of times when trail mud and grime has been burned off as I drive - and it is not a flower like smell

I have checked everything you posted above and 2 of my local dealers claimed to look also. They agree it kinda smells like the cat but its not to the rotten egg smell but close. They also said they can't do anything about it until it clogs or throws a SES light. If the windows are up and the hvac isn't bringing in outside air then the smell is gone. It is definitely something exhaust/engine related but can't seem to find it

Try some sea foam, might help clean the engine out some.

Also try running regular gas. There is no reason to use high octane gas in an engine that does not call for it. High octane gas is for high-compression engines that are designed for it to prevent pre-detonation. With high octane gas, you may be firing late, causing unburned hydrocarbons, causing a rich fuel in the exhaust, which is burning in you catalytic converter, casing the smell.

It may take a few tanks to subside.

High octane gas is not better for a vehicle that calls for regular gas...it just cost more and gives you poorer gas mileage.

I ran regular gas for the first year we owned it and thats why we switched to 93 to try and make the smell stop and never switched back.

How do you guys do the sea foam on these. Add to gas tank, crank case and suck it in a vacuum line? if so then what vacuum line?I have done it plenty of time on my supercharged grand prix but never on this car

I suck a little more than one-third of a can in a vacuum line going directly into the plenum. I'd tell you which one, but I don't have a second gen, so I can't look to get specific. A few revs, and it really cleans it out

I put the rest in the gas tank. The only time I put it in my crank case is just before an oil change. I know it says you can leave it in there longer, I just don't like the thought of thinning my oil.

Having said that, while it will clean out your injectors, I doubt it will solve your problem.