Bank 1 and 2 lean

I belive the code is P0171 and P0174.

I also only run Mobil or Marathon gas through it and it is all 87 octane accept for the occasional Premium/93.

Will smoke testin act the same as checking the vacuum lines with break cleaner?

But would a leaking vac. Line or intake mannifold cause the light to continue to go on and off?

I have been waiting for this to happen again.

I have replaced the MAF, TB gasket, Fuel Filter, Plugs, Wires and all that good stuff.

It has been warm latley, (40-50F) and my truck doesnt throw the P0171 and P0174. But again the other day the temeperature dropped and now the truck is throwing both of those codes again. I have been running at least 83 octane fuel and have looked for vacuum leaks but am not sure of all the vacuum hoses to check. My next step is the replace the EGR valve and the cooland temperature sensor. Would these be a wise decision or what would be casuing the problem?

But if it were a manifold leak would the SES light continue to go on and off over the course of a few days, especially when the weather gets warmer? Seems as though the gasket would either be cracked or not and not cause the light to continue to go on and off.
Also if it were the injectors would I experience a lack of performance in acceleration or power? I currentley am not experienceing any engine difficulty accept for the SES light.