fuel delivery problems

I have been having some problems with the fuel delivery to the engine and cannot seem to narrow it down exactly. I belive it to be fuel injector related, but want to see if anyone has experienced the same problems.
In the mornings when I start the Jeep and drive the first 2-5 miles I get alot of hesitation in the engine. I will keep constant pressure on the pedal, but the engine sputters and almost sounds like no fuel delivery.
The problem goes away after the Jeep is warm top an extent, only at speeds between 0-50. At speeds greater than 50 it acts the same way. I can be cruising along at 60, 75 (whatever above 50) just fine, then when I hit a hill or need more power the engine sputters first and the goes on. It happens with or without the cruise control on.
Now the crazy thing is that when I am in altitudes greater that say 5500 - 13000 ft, there are no problems at all. The Jeep runs great, has a ton of power, and gets excellent mpg. I live in Texas however so those are not the normal operating conditions. I alternate between working in Colorado and Texas and did have not had this problem at all in CO. I would make trips home and get just south of Santa Fe, NM and the problem would start again and annoy me the whole way back.
It has been doing this for a year or so. I have replaced Fuel filter, cleaned the injectors, checked exhaust leaks, vaccum lines, rotated octanes, cleaned the TB area, etc...
Any ideas????

Thanks in advance
Steve

tough to say, first thing I would have said is fuel filter, but you did that. Maybe Fuel pump or sock or possibly a vaccum leak.

sounds like some problems i had last year, if i were you i'd try the ballast resistor, its a $5 part and it can cause the problems that you are describing. its the little ceramic peice on the drivers side fender, the computer routes voltage thru the resistor to the fuel pump to make it run quieter, so check that out and get back with us.

Could also be a MAP sensor problem. At high alt. it may be working just fine since there is a bit less air to work with. Maybe take a look at the vac line running from the TB to the MAP.