Rebuilt magnum 360 Noise

Sounds just like an exhaust leak to me. Was the exhaust system moved from the first engine to this one?
The exhaust system is the same as the old one. Same manifolds and everything. Funny thing is the other motor had a similar noise. Slightly louder but the symptoms were the exact same. Only made it holding the rpms below 2k. Two different motors. Similarish noise with the same symptoms.