I have a 1994 GMC K1500 sierra sle 5.7L V8. The other day I started the truck, let it warm up for about 10 minutes and put it in reverse to back out of the driveway and it had no power and almost stalled. I put it in neutral, it seemed to rev up fine so I tried reverse again and same thing, no power and wouldn't rev up at all while in gear. Today I just changed the fuel filter, spark plugs, distributor cap and rotor and changed the oil and it still doing the same thing. I had to put it in first gear and 4low just to drive a half a block to my buddy's shop and it stalled 3-4 times on the way. The truck starts and idles fine but as soon as I put it in gear and touch the gas it bogs and almost stalls. I should also mention that the check engine light comes on when the key is in the "on" position but does not stay on when idling. Any ideas or help would be appreciated. Thanks in advance

 

I have done some google searching and found a couple of things to check. One of them is check the fuel pressure but I'm not sure how to do it. Can someone help me out? Thanks