Help engine pinging

[lander31]

I have a 92 x with 105000 miles on it an it is pinging bad. I have did a search and read the other post. Here is what I have did.
1. Installed new MAF
2. Installed new plugs and wires.
3. Installed new fuel filter
4. Run two cans of Techron thru it.
THings I have found.
The # 5 plug is fouling out. It is not oil fouling but a grayish coating on the plug. I thought at first it could be antifrezze but I have not been loosing coolent.
The compression on all cyl is good around 160.
Plugs 4 and 6 are fine.
The engine will start pingin bad after it gets warm. Not when it is cold.
I have pluged the engine in to a diagonist twice and have no error codes. I have took WD 40 and sprayed it around the mainfold looking for leaks and checked for vaccum leaks.
Can some one give me some idea on how to get rid of the pinging. I am about ready to take off the mainfold and check for blown gaskets. I am about at my whits end trying to figure out what is going on.
Thanks

 

[mrboyle]

Check the intake tube between the MAF and the throttle body they can split in the flexable area and cause the engine to ping.

 

[Billy177]

try some sea foam

 

[Lemondrop]

Your intake gasket might be leaking , vacuum leaking internally . Check the intake bolts to see if any are loose . From what I have read it is a common 4.0L problem . My 95's bolts were loose but had not caused any problems yet . I was reading the forum here and saw someone with similar problems as you that tightened thier intake bolts . So I checked my bolts and sure enough the bolts were loose . Im about to hit 130,000 with no problems with the engine .
My HCU for the ABS crapped out , and I lost my airbag monitor but no engine problems .

 

[lander31]

Ok;
I tried the sea foam twice and it help some. The engine still pings but nit as bad. It will start pinging when I get over 60 mph. I also checked the intake tube between the maf and throttle body. It look fine. I will have take off the top of the intake to check the bolts. So I guess that is next, I can not get to all of the bolts unless I take of the top part of the mainfold. Any other Ideas.
Thanks