lost of power

[Gaucho]

hi guy's,,,, well here's my problem but just so u know,,it's a 89 GMC fuel injected 350 i've changed plugs, wires, coil, cap, rotor and ignition module... cleaned the fuel injectors and changed out the gas tank and inline filter...

then i installed a MSD 6AL with wiring harness,, i notice some new found power but within a couple weeks it disappeared,, so i disconnected the MSD and put it back to stock (which worked before the MSD) to see if the power would come back and the dam thing won't start,, fuel injector's are pumping in gas but there's no spark... so i put the MSD back on and it started...

what i did notice with the MSD hooked up is it seems to lag like the advance isn't working,,, what controls the advance??? i know the computer does but what activates the comp into controling the advance???

thank's in advance