Surging problem/Sensor readings at idle?

[Kimppu]

I have little surging and bucking problem in my '96 4.0 OHV when driving steady at 1500-1200RPM. I think the engine is running lean, because it gave the code P1131 once. I have cleaned the MAF, IAC and changed TPS sensor without any help. Now I like to know what the readings should be in MAF at idle and how big difference is allowed in long term fuel trims between bank 1 and 2. Bacause I think that the O2 sensor might be bad in Bank1.

My sensor readings at idle when engine is warm:

RPM 812
MAF 4,6 g/s
Timing advance 17,5 deg

Long term fuel trims after 50 kilometers run

Bank1 -3,2%
Bank2 -0,5%


BTW just to make sure: is the Bank1 passenger side?

Thanks