21 doesn't seem like enough to throw afr off that bad. To check the exhaust side just duck tape your air hose into the tailpipe and then same procedure as intake manifold.
Are you showing any misfire counters or anything? Mine doesn't hardly ever but it's a thought since misses or a dead hole will swing afr to the lean side and I've had my car run smooth as hell on 5 cylinders and the only way I could tell was listening to the exhaust closely for a little chuff in between pulses.
Are you showing any misfire counters or anything? Mine doesn't hardly ever but it's a thought since misses or a dead hole will swing afr to the lean side and I've had my car run smooth as hell on 5 cylinders and the only way I could tell was listening to the exhaust closely for a little chuff in between pulses.