Q: Car sounds rough...replaced clutch with no luck. Magically fixed today, but airbag sensor is on

Hey there, Alright here is a tough one. Over the last few months, my honda civic 2006 DX has been sounding tough. It drives fine, but louder. When you accelerate quickly especially out of 1st and 2nd, it would be very loud. The best way I could describe it would be that the engine is "sucking air" when high RPMs. I brought it to the mechanic and thought it was the clutch (87000 miles). It wasnt, but said the clutch was going on it (manual transmission). Sound remained and got a second opinion and thought it was the transmission, even though I have no problems shifting. Another friend thought it could be a bearing that needed to be lubed...I'm personally not a mechanic. However today out of the blue, it sounds almost perfect...sound gone! However coincidently, a new light popped on for the airbags to be checked. Previously over the last 5 years, I have replaced (2) O2 sensors

My car has 87000 miles.
My car has a manual transmission.