Check engine light and loss of power?

Well i just did glow plugs and uvchs truck seems to be starting good but now i have a check engine light that comes on and off and when its on the truck has a big loos of power...the light only comes on for say 30 seconds then goes out and during those 30 seconds the truck has no power then once the light goes off the power comes back any ideas?

Well i drove the beast a little more and the light hasent came back on and the truck is running good so im not really sure what the deal was.

If your CEL came on, you can scan the truck for the code to see what it was.

Ya i dont have a scanner good enough my cornwell says no codes found. I will have to use a buddys to see what codes a stored.