Help Pinpoint Problem (Code 51)

[shiftdrift06]

Driving today, I notice my A/F gauge stays in "lean". Then a CEL light. I drove home, I smell fumes of gas, and other stuff I can't pinpoint.

I use my dads scan tool, And came with code "PO171 MOD 40(Code 51) SYSTEM TOO LEAN (BANK 1)"
I did a parameter check WHILE IDLE and here the results, tell me something looks out of place.

ABS TPS% 6.3
RPM @900
COOLANT 190
Calc Load% 5.5
MAP "Hg" 12.1
IAC @115
IGN ADV DEG @5
LT FTRM% 24.2
ST FTRM% 24.2
FUEL SYS1 CLSD
O2SS11 (V) 0.040
O2SS12 (V) 0.550

Any Ideas what it might be? "Map, O2, CAT, Injectors, etc.." Which one more favorable you guys think?

 

[Shadow98]

Are we talking about a narrow-band A/F guage? If so, try replacing your o2 sensor, it might be going out.