This could be coincidence but about a month ago I was driving in heavy rain and my air/fuel gauge starting to show my engine leaning out and it was losing power and its pretty much did it ever since. It will start to run lean then go back to normal and it will do this several times while I'm driving. Also it seems alot of times if I open the throttle at least halfway the air/fuel ratio will go back to where it needs to and the car runs like normal. Could one of my oxygen sensor be going bad? or maybe a clogged fuel injector? Thanks for any help.

 

What type of A/F ratio gauge are you using - narrow-band or wide-band? Where is the sensor installed? Does it pick up the combined exhaust of both banks, or only one bank?