Service engine light blinking.

I have a 2000 2500 silverado 6.0 4x4. Out of the blue one day the service engine light just came on and started blinking, and not it does it all the time,but it only comes on at 45 mph and higher. I hooked it up to a computer and it told me it was misfiring. Iv changed wires, plugs, ignition coils. and still no changes. does anyone have any ideas of wat might be causing this problem.  

which code was it?????  

i dont remember the exact code the guy that was looking at the computer told me it was a misfiring code.  

change your fuel filter..... if it is restricted bad enough it might lean out the motor above 45...   remember... the fuel goes through the filter again and again.

see if there is a fuel pressure test port...   have the pressure tested...

get the codes read again...   obd2 code readers start at 39 bucks.. decent obd2 scan tools that read live data start at 130.. over at harbor freight.. #98614 does read live data ..

autozone has a decent repair manual online for free that covers that model..

http://www.autozone.com/shopping/repairGuide.htm         put in your model data..  

iv changed the whole fuel system and everything. but I fount the problem this morning. I did a compression test on it this morning...2 hours later I fount out Iv got a bad head. Went to advance to get the heads and they told me $1,300 for a cylinder head.... ouch. So im thinking bout just getting them rebuilt or going and buying a whole new engine.  

any body know where I can get a good set of heads for my truck