2002 ford explorer with seven ob2 codes

[towncarblue]

my girlfriend has a 2002 ford explorer xls 4x4 4.0L. she bought it used a while ago [about a year] . i recently went and checked the service engine soon codes
and received these.
p0171 -System Too Lean (Bank 1)
p0300 -engine misfire
p0304 -engine misfire
p0305 -engine misfire
p1131 -Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1
p1150 -Lack of Upstream Heated Oxygen Sensor Switch - Adaptive Fuel Limit - Bank No. 2
p1151 -Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 2

and according to the scanner this one is pending.. p1132 -Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Rich - Bank No. 1
could all these codes be related to a single problem"?
what do i need to replace? what should i start replacing?

 

[matt0248]

If I had to guess I would say that the intake manifold gaskets are leaking. Most likely around cyl's 4 and 5 causing the misfire codes there. This would give an extremely lean running condition with goes in line with the other codes that set.