well no
it is basically saying your cat is fubar however one of the codes saying the lambda is not switching correctly, i am unable to determine whether it is the front or rear
p1133 Heated Oxygen Sensor (HO2S) 1, bank 1 - insufficient switching
p1171 Mixture control (MC), engine under load - mixture lean
Fuel system - lean mixture during acceleration
p0420 is either your running a sports cat or your cart is fubar
most people on here say that the cat / rear lambda will not affect fueling 😛
a cat on a vectra B will cost around £100
you will need a new gasket for manifold / downpipe - £5
new front lambda is £60 - NGK - fit yourself
same price for rear maybe slightly more expensive due to length of wire 😛 - NGK fit yourself
£230 to replace everything is hardly expensive