Starting to do some upgrades but need advice. What are some options on freeing up the exhaust for a '90 xj, especially from down pipe on back, and what headers work. I can see that '91 and later won't fit.

 

You are limited on header selection. Is your current exhaust manifold cracked?

One of the single best mods you can make is having the stock downpipe replaced by one that doesn't have the "crush" in it. If you're lifted, the pipe can be routed like stock. If not, have a muffler shop make and install one and route it to clear the front driveshaft.

 

No cracks in the stock exh. manifold. The xj is not lifted and no plans in the immediate future to do so. If I have the muffler shop fab up the down pipe how big should I go, any suggestions and in your opinion would the benefits gained be worth the expense.
Thanks

 

Stock size. Just have it built the original pipe diameter without the "crush" and routed to avoid the driveshaft. Take a peek at your downpipe and you'll see what I mean.