I drive a 89' Jeep Wrangler with a 258. I have replaced the carb. with a holly to stop the common problem with the carter. I have also replaced my muffler with a Gibson to help a bit with performance (the old muffler was shot as well).
Here is my issue. The f'in thing stinks. I take off the top and the smell on the fumes is horrible. I don't know if this is a common problem with Jeeps, but I feel like it is going to knock me out the smell gets so bad. The 258's in 89, maybe other years as well, have some crazy emissions set up with hoses running all over the place. When I put on the new carb I had to drill some holds in the top to run in the back flow exhaust. If you follow the hoses to their origin one will find a one way valve that is involved with the exhaust.
Anyway, just wanted to throw in as many detail as I could to see if anyone had the slightest idea as to why my Jeep smells so bad. By the way I take two showers a day and use deoderant, so it aint me.