Stock exhaust note question

I have the 4.6 stock on exhaust and I notice when getting on the throttle, I hear what sounds like glass pack exhaust notes starting at around mid range. Other times I do not hear it and it's a smooth roar. Is this normal or do you think I have a leak?

 

It’s likely a normal sound if it’s intermittent. Our trucks have variable valve timing. So depending on the cam profiles the engine will change its spound

An exhaust leak would have a ticking sound anytime you’re on the throttle. It would never go away for the most part. Unless it was a cracked manifold. Then it woood only leak when cold but go away when hot.

If you have anymore questions and wanna call my number is+17608774234

Keith

 

Thank you for your help. It's cool outside currently here in central Florida and I can't replicate the sound. I will try again when it gets warmer this weekend but it sounds like a BAM muffler when it happens. I've only had truck since last October so not sure if it had been that way from the beginning. I did change my oil using the recommended 0w20. I'm wondering if the previous owner used thicker oil because I noticed my mpg went up from high 12s to mid 14s now. Perhaps the thicker oil was the corporate?