Quick help needed - exhaust leak?

[TX99M3]

I just installed high-flow down pipes from VRSF on my 2013 335is. I ran a bubble test for leaks and there is a slight leak (few tiny bubbles) where both downpipes connect to exhaust and a slight leak around each O2 sensor. Connections to the turbos themselves appear fine. I used new gaskets and all is as tight as seems feasible. The O2 sensors will not budge further. Should there be absolutely no bubbles or are a few to be expected? If there should be no bubbles, what can be done when the O2 sensor are as tight as they will go?

Before you ask - I did get a faint smell under the hood and maybe in the cabin during a short test drive but I'm not sure if it was exhaust or some type of initial burn-off from the new downpipes.

If I need to find a way to fix this, I'd like to do so before I put the belly pan back on...

Thanks to anyone who can share some quick wisdom!

[TheJuggernaut]

If you mean you sprayed soapy water onto exhaust components and ran the engine, the bubbles will be the water boiling off... exhaust leaks should be investigated with a smoke test.

[TX99M3]

I did use soapy water but the engine was cold. I applied air pressure via small shop vac blowing into one exhaust tip with the other tip being momentarily restricted. I don't have the equipment to do a smoke test. However, I did take a longer drive today and did not notice any exhaust smell in the cabin.