First off the cars a 98 formula has 133k on the odo oil hanged every 3-4k with mobile 1. On cold start the car will see 40 psi then when warm and cruising around 30ish. My main concern is when Im at a light the pressure will hover at 20 and sometimes feel like it has the ever so slightest miss. The car got brand new ir55x plugs and new wires about 10k miles ago. The car is also primarily bone stock with the execption of gears and a loudmouth. What oil pressure do most high mileage ls1's get at cold start,cruising, and stopeed at a light? I purchased the car with 105k so I cannot vouch for the care it received before I bought it.

 

It's within spec, but me personally like to see it around 40psi warm and at idle. One sure way to check is hook a manual oil pressure gauge to it. You could have a faulty sending unit.