2001 Chevy Blazer Start takes a few seconds

2001 Chevy Blazer 4.3l engine. Often the first start of the day takes a few seconds of cranking then it fires, runs fine afterwards. Sometimes, even after the first start of the day it takes a few seconds but ususally fires immediately. Replaced fuel filter (it was due) but I figured that wasn't the problem. Tested fuel pressure it reads 58lbs with key turned only, running it reads 54-58lbs. I suspect the fuel pump check valve is shot (had a similar problem with a past Jeep fuel pump 2x). While running when you step on the throttle it drops to 52-53lbs but recovers to 58 after a second or two. When you hold the throttle open it does stay steady about 58lbs. I'd also like to verify the fuel pressure regulator is good or bad. Can the regulator be tested and if so, where is it (I know its by the intake manifold but exactly where I can't determine).