No acceleration?

I have a 95 gmc sonoma 4.3l tbi. You guys seem more helpfull than the sonoma forum so I'm posting in here. So anyways within the last year I have longblocked my motor, replaced everything under the hood, and had the trans rebuilt. When I was doing my motor one of the guys helping me said he thought my fuel pump was going bad or my filter. So here's what it does. If I'm at a light and stomp on the gas to take off the truck makes a nice initial jump but then pretty much falls on it's face like it wants to die then after a second or two is takes off again. It almost sounds like it is starving for gas. Then While I'm driving if I stomp on it to pass someone once the engine gets above 3,000 rpms its makes all kinds of popping and sneezing noises out the intake. So That also sounds like it is running lean. So have any of you guys had this problem or know what it could be? Thanks for any help.

I would check the EGR system/ change the fuel filter/run a couple cans of inj. cleaner /check fuel pressure.
pumps usually work or dont.....usually. but it sounds like your heading in the right direction.
keep in mind a lack of fuel can also mean an abundance of air(vacuum leak)

its a good idea to check volume if the fuel pressure checks out. get a 20oz soda bottle and run a line from the inlet side of the fuel filter to the bottle. a good pump should fill the bottle in about 15 seconds. if it takes longer then your pump isnt putting out enough volume. that has bit me a couple times. you can check injector spray with a test light. hook the test light up like youre going to check timing then point it at the injector spray and look at it. it should be a nice cone shape with no sign of big drops or a non-coneshape spray pattern. keep in mind low fuel pressure or volume will mess the spray pattern up too. but check it at various rpms.

Thanks for the replys. I thought I could here a vacuum leak but I took an unlit propane torch and checked all the vacumm hoses I could find and the engine never changed rpm or sound. So I just figure the whistling sounds was because I took off the air box and could just hear the intake noise. I will try some injecter cleaner but I think after next weeks pay check I'm gonna do the fuel pump and filter if we don't get more snow. It is only like 45 for the pump and 6 for the filter so it's not too bad. Originally I was just gonna but a fuel line pressure guage for like 35 bucks but now that I know the pump is so cheap I will just do the whole shot. When I longblocked the motor I replaced the egr which wasn't cheap. I think around 90 bucks from the dealer, so I don't think that's it. So after I change the pump and filter if it is still doing it what else should I check? Or are there any hidden vacuum lines I should look for?