4.6L exhaust noise

now i always had 5.0L mutang and the other day at a dealership i noticed the 3 4.6L's i was looking at all had the same poping sound at idle comming from them sounded like the right side tailpipe, not a miss but almost similar in sound and the cars ran great and the was no poping sound other then idle...is this a normal sound on these motors?

What year, I never noticed it on my 2000.

I never noticed a "popping" in my '97.

96-98 body style