oil pressure 2.7

Hello- my 07 Taco has developed a problem recently. The oil pressure light has been staying on longer when starting cold. 0 or colder and flickers intermitantly while driving. At idle it's fine, after it's been warmed up the light goes off right away. Any ideas? I'm hoping sending unit but wondering if a bad oil filter(ADBV) could be the issue. 37k miles my clutch is chattering alot also and the dealer told me this morning they would'nt be covering it. This is my 4th Toyota my only brand new one- and it's been my most troublesome- starting to lose my faith in them. ARGH

 

So I changed my oil filter tonight after work and it fixed everything- which is nice but also worrisome. I had about 700 miles since an oil change-Amsoil 0w-20. Either the oil filter was clogged or defective? I'm going to cut it open and check. So my question now is-What was the noise I was hearing-my engine being starved of oil? Or would the bypass valve make chattering clicking sound? I hope thats what it was? ANy input appreciated.