Rattling noise under hood - 98 Freightliner cat c12

So here is what happened

I didn’t realize the truck had low engine oil in it (yes stupid me I should have checked it before), and realized a rattling noise being on higher rpm. So topped up the oil and it’s good now. But the rattling noise is staying. Usually happens on higher gears and higher rpm. When I drive 50-60 mph, I realized when I touch the clutch down just a soft touch down, the rattling noise goes away. There is no noise being in neutral and parked.

Then again, I just fixed a leak on the exhaust under the hood and to be honest the guy did a horrible job welding it which I would like to get re-done anyways.

what could be my problem here. Any help is much appreciated!