Start with a heavier oil and then check the oil pressures. With these motors it seems that the first symptom of low oil pressure is ticking lifters and rockers, not a bearing knock from the bottom end. Seeing as how you have an '03, a cracked oil pump is a good possibility. That noise would come from the timing cover. If you aren't able to pinpoint the exact source you need to find a shop that can. The price for an installed oil pump isn't cheap but it's much cheaper than a new motor.

Posting a bid of the noise might not be a bad idea.

 

change the oil and put a oil pressure gauge on it

 

Thanks for the tips guys. I'll dump the oils and take it from there.