My only suggestion is to make sure you "Purge the Exhaust Tube" with a proper mix of 'welding gas' (Tri-Mix?)... usually makes the inside weld come out extremely smooth... and the inside weld is where it counts on exhausts and intakes... have a bunch of mountains on the inside of your exhaust pipe is not good...
As simple as using some tape with a few holes poked in to 'purge air out and get your gas mixture in'
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