pO306!!!

Hi all,
I apologize in advance for the lengthy post, i wanted to be as thorough as possible as i have had so many different diagnostic darts thrown my way in the last few months.
My 05 v6 tundra has 175 thousand miles on it, it has been maintained well over all and has always been a steady truck. A few months back it developed a slight shake/strong vibration at start up, very intermittently, but always on cold starts. Once it warmed up the truck idled fine and ran normal.
Finally, after about a month of these random funky starts, I started it, put it in gear, as I did that it sputtered, I gave it a little more throttle it worked through the choke but check engine light came on. I was yet to see that light and was perturbed, I immediately went and bought code reader anxious to pinpoint a problem. p0304, I researched that and decided to give it new dgk plugs and even bought 6set of coil packs online. All was good, no obvious sign of foul plugs (cyl 4 plug looked fine as well) so i proceeded to replace plugs and coil packs, started and ran great..for a few weeks.
Until one morning before work i went to warm it up and when i came back out, it threw a code again! This time I got p0306. I found that a lot more issues fall under this code? I have a friend with an auto repair shop and when i ran it by him he had me do MAF and clean the throttle body, surprising myself, I did that with no issues. Again, code reset and truck ran great...for a few weeks..
So that is where I am at as of now as far as repairs, now the truck will go through week running and starting just fine, then randomly throw the p0306 code one morning. The truck will get bad mileage whenever the light is on, this will go on for a day or two then i start it, no light, truck runs fine, normal mileage..
There is a list of scary things I have heard (heads,head gaskets,cpu) and just wanted feedback from any one who has seen this troubling issue .. THANK YOU