Gas gauge gone nutty, Advice please

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I just bought this TI and I filled the tank when I got it two weeks ago,
There have been no issues until last night, I was at 1/4 tank and it would read 99 miles to go on the display, I had to drive to work for an emergency power outage and it was raining pretty good, Only 5 mile drive,
A couple hours later I drive the 5 miles home now in a drizzle and when I pulled in the drive way I noticed that the fuel gauge was reading nearly 3/4 tank and reading that I could go another 150+ miles,,,
So something had gone wacky with the fuel gauge system.
Where would I look first?
I am assuming a connector somewhere is getting wet and causing this issue,
But being new to BMW I really have no idea where to look first.
Thanks for any advice you may have,
And yes there is about 275 miles on this tank so I know it's not at 3/4.
Thanks !
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Peter