Hi, I'm new to the site. I have an 04 Yukon 2500 6.0L with 123,000 miles, that has an oil pressure issue. I have had it to the dealer and still do not know what the problem is. The oil pressure gauge reads low. Low enough that the low oil pressure chime comes on at idle. The sending unit has been replaced. Did not fix the problem. The dealer is telling me that the oil pressure reading at the oil filter is 35psi and at the sending unit it is only 8psi. What would cause the oil pressure reading to be significantly different from the oil filter to the sending unit? It had lifter noise. Dealer diagnosed it as a collapsed lifter. Paid 1350.00 to have lifters on left side replaced and new oil pump installed. Did not fix the problem and still makes lifter noise. GM Tech service is saying to tear down the engine and inspect?? Any ideas? Thanks in advance for the help.