P0170 Mitsubishi -

Question

Hi, this car is rapidly trying my patience. I did have code P0300 which has now been fixed (I hope) but now I have P0170. So far I have:

1/ replaced the MAF sensor unit
2/ replaced the throttle body block with sensor
3/ replaced all plugs
4/ replaced all filters
5/ replaced the PCV valve
6/ replaced the fuel pump
7/ had the camshaft sensor checked - it is ok
8/ had the valve clearances checked - ok
9/ Intakes checked for air leaks - no apparent problems

The car starts well, ticks over well, runs well on petrol and LPG gas, does not perform erratically, returns a reasonable mpg and shows no obvious reason for the service light coming on. Help please - Gordon