Bought a K&N air filter. cold air system. I have a 1996 850 T Wagon with 250,000 miles. Filter gives car a lot more zip. There is a bit of intake noise and a sucking sound when you back off gas.
Now the problems. On Full throttle blast car cuts out for a second on the way to hyper speed then resumes.
In stop and go traffic engine starts to miss a bit at first and it gets worse and worse till it is really missing as you accelerate. Sometimes get check engine 172-too rich or engime knock sensor codes.
I tried Premium gas. no help. It have been below zero here and maybe the intake air is too cold? Removing the air box does get rid of temp compensators.

anyone had similar problems. any Ideas?