I bought a 99 323i with codes????

[jcstiner]

Ok so I bought a 99 323i and the guy said it was his sons bla bla bla. Well he has custom headers so I don't think there is a port for the o2 sensors. So I think the first four codes are because the o2 sensor isn't connected and the forth I'm hoping is a spark plug or coil pack. My question is will a tune fix the first 4 codes? And if not what are my options??????? The car runs but at idle it bogs down to the point it stalls. All intelligent opinions welcome.
P0135
P0161
P0141
P0155
P0306

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[zippy320]

You also have a hole in your front bumper? Is that like a cold air intake or some sort ? Maybe its interfering or giving incorrect readings on the amount of air coming in ?