possible oil pump problem ,slow oil pressure on cold engine

I dropped an earlier post about engine noise on warm restart of 2003 silverado 4.8 engine.appearing at 8000 miles and third oil change.GM changed the o-ring on the pickup tube of the oil pump per TSB this did not help.also appearing at the same time as the engine noise my cold start oil prerssure is very slow, taking 4-5 seconds to max out where before taking 1-2 seconds at tops no matter how cold it is outside even 30 below zero.could it be the pressure relief spring in the oil pump stuck or broken causing my two problems or could it be a spun bearing.the engine runs as strong as day one. oil pressure on the road is the same but idle dropped about 5 psi now about 30psi at idle with warm engine.gm says they will change the oil pump. any thoughts?