Is there a way to tell if I have a restriction someplace in my 91 244 exhaust?

I ask because the flow is nothing like the flow on my 89 740 (same engine) and my friends 84 240 (B23F) My 91 in question does have over 300,000 miles though....is that a factor?

It flows but seems quite restricted by about half the other engines mentioned.

Please note: None of the above engines have a catalytic converter. So, what way can I test to see if either my resonator or muffler or perhaps both are clogged? No loud noise or puffing on the mufflers are present. Engine seems to run good....I just have a hunch. I also should mention I don't get a nice cold weather vapor flow out the back especially when giving the car gas when going up a hill etc.

Thanks..