[Shotimes] Help! Loss of Power Round 2!!!

[Shane Graham]

Some of you have responded to my first email about my loss of power problem.  First of all, I want to thank everyone for their input.  It is greatly appreciated.  Let me explain again what is happening.  In the morning when I go to work, I usually have full power.  But after work, heat may be a factor, I seem to lose 40-50% of my engine power.  Almost like it is running on 4 or 5 cylinders.  Sometimes I will have full power and then it will pulse or rapidly lose power and gain it.  The tachometer acts sporadic but never drops to zero.  When it is acting up and I stop at a stop sign, the engine will idle rough but never die.  Here is a list of things I have either checked recently or replaced within two years:
 
1.  Just checked the fuel pressure idling and driving.  It averaged 38 PSI and never took a big dip.
 
2.  Checked a lot of the electrical bundles for a possible short to ground (Don's suggestion).  Did not find any.
 
3.  Replaced the spark plugs and plug wires.
 
4.  Noticed when checking the fuel pressure that I have a lot of air in the system.  Also, when I release my gas cap a bunch of air is released.  This didn't seem right so I drove with my gas cap loose, but I  still had a loss of power....??
 
5.  I do not have an aftermarket chip.  (Don had me check)
 
6.  Put a new fuel filter on.
 
7.  Installed a new air filter.
 
8.  Cleaned the throttle body.
 
9.  Swapped out my MAF sensor with another used one and had the same response.
 
10.  Less than two years ago, I changed the CPS and the Cam sensor.   
 
Shylo suggested that it could be my DIS module.  This is a good possibility, but I priced one today and they cost $175.00.  I really want to make sure it isn't something else before I spend that kind of money on a part!  It seems like it is electrical now, but at this point I don't know what to think!  Any other suggestions or comments will be much appreciated.  Again, thanks for your previous time and help.
 
Thank you,
Shane Graham
91' White MTX