Well it was around 95-100F outside, and engine temp was at 90C. Hmm how hard is it to check for the compression loss? any special tools needed that are hard to get? and how much would it be to fix? someone on another forum suggested a new muffler... below is his post

Yes, a loose baffle inside a muffler, flapping around could make the noise you describe. it could also partially block the exhaust flow, causing sluggish performance, AND an overheating muffler. I bet it's an easy fix with a new muffler. JMO. Good luck.
Bert

what do you guys think about that.

Dan