Erratic Idle?? help please

[Thatlowchevy]

i recently put a new engine block in my 1998 vortec 350, it goes from idling around 700 RPM to 1200 RPM alot. i was wondering what would cause this erratic idle and what part i should focus on. i was told many things from the MAF to the TPS and i am confused lol

 

[DAC_CFH]

check all the vacuum lines?

 

[Thatlowchevy]

I've checke deverything i know to, still nothing