Yup..there would be "detrimental" effects. You would get the sugaring mentioned. This can lead to voids or cracking. ESPECIALLY in a high vibration situation like this exhaust. If you can get in to clean it you could use Soar Flux if the weld is only one pass. Solar flux is highly corrosive and can actually weaken a weld joint if it is not removed with warm soapy water and a stiff brush.
You cannot believe the difference if a SS weld is back purged or just "left to the wind" . The backside of an unprotected weld is ugly.
I have tools I don't even know I own...