98 4.0l Sohc

[Wrench]

Well I've switched from a 97 4.0L OHV explorer model to a 98 4.0L SOHC XLT model - 97 was about to grenade the TC.
I have a cold start problem when vehicle rests overnight outside. Engine will start and continually surge between near stall to 2500 rpm for about 10 minutes when weather is below 45'F till engine starts to warm up then the engine smooths out and goes slowly back to 600 to 700 rpm idle. If I use the block heater overnight the engine will start and high idle properly and ease back as it should to normal idle.
I pulled the IAC and it looks pretty clean, checked the air intake filter (its brand new) pulled the intake rubber tube to look at the throttle body butterfly and throat and it is also pretty clean. I gave TB housing a light cleaning with TB fluid
MAF sensor looks clean although I did not remove it from tubing. Checked for any codes stored - none. No CEL
MY thoughts on it - If engine starts there is good fuel pressure and there are no issues when engine up to operating temp. Inspected one sparkplug and it looks a bit worn but still serviceable. Checked the PVC tubing and for any obvious lose hoses for vacuum leaks. Checked fuel pressure regulator tubing for gas residue -none. This engine runs like a top when warmed up a bit but let it sit overnight and it acts up cold only. Could the coolant temp sensor create this issue. Any thoughts or suggestions would be welcome.

 

[Wrench]

Is 57-73 psi the correct fuel pressure range for this engine and year. My Haynes book says 30-45 psi with vacuuum hose connected and 40-50 psi with vacuum hose disconnected.It is a return system with fuel regulator. I also note that ony one side of the MAF sensor has a torx anti tamper bolt and the other side has a black molded plastic cap on what looks to be a rivet. Could this be the cap that some members say to pry the material off and there should be another torx head bolt. Sure wouldn't mind giving the MAF sensor a shot of electrical cleaner.