2006 G.P. Series III V6

This happened out of the blue nothing leading up to the problem/s. Recently having issues with rough idle and under power. I've researched i.e. clean throttle body OK, clean MAF sensor OK, check air filter and check MAP sensor which I had to replace because it was cracked and scan OBD2. Had the scan at local parts store and came up with PO300(ignition system, misfire related) & U1000(data link malfunction).
I don't understand is when I start the car there is no engine light or DIC message, the car still idles rough and when I give gas the engine light comes on and I proceed to drive the light starts to flash and steadily runs rougher. Any suggestions are welcome, thanks.

UPDATE: Had to take it to the shop the ICM, all coils, plugs and wires replaced. Along with the clean MAF, Throttle Body and new MAP sensor she runs great only 1,300 later.