My xg350 with 208,000 miles started losing power when climbing hills and accelerating to get on highway. It finally threw code p0154 O2 sensor (B2 S1) which I replaced. The car is running much better but still losing power on hills. It just threw code p0320. I had my timing belt replaced last year and the mechanic said he accidently broke the crank position sensor. I wondering if he replaced it with an aftermarket part that has now gone bad. Does any one have any thoughts on this? Thanks!