I'm getting close to finally making a decision about this exhaust I want to build out.I just installed some long tube headers and I definitely want to go two into one.

But I wonder... if you join the two into a single pipe, and then into a single inlet for a 1 in, 1 out muffler, do you lose the benefits you see in regard to better airflow, than if you go into 2 inlets into the muffler?

I really like these Magnaflow mufflers but It one comes with a one in, one out configuration. Otherwise, I'll prob go with Flowmaster 40, which has two in, one out.

You've answered my question, then!

Don't get too hug up on performances losses. Most aftermarket exhaust systems are oversized for the average engine's performance.

I ran 2-1 exhaust, 2.5" diameter all the way with a decent 351W. Never felt like it was missing anything over the 3" exhaust it had prior.

Remember Bronco's are really short too and piping restrictions are a function of length/diameter, so a smaller diameter pipe over a short run will have comparable restriction to a larger diameter over a long run. If you have long tube headers, the 2-1 collector will likey be behind the t-case, the single exhaust from the collector to exit will only be 4-5 ft.

One other benefit to going smaller is packaging and noise. I'm running a 3" and have had a hard time quieting it down. It's OK now, but took some work. You can also get tighter bends in a 2.5" than a 3", so wiggling it around the rear axle is easier.

Great tips - appreciate it.