Coolant on the intake and P0171 , Silverado 2008 5.3

[F.Reyna]

After a head lifted misfire repair , my truck begun to loose coolant and check engine is on , my scanner show p0171 , to learn bank 1 ,and occasionally p0300 random misfire ( pending) , and I don’t have coolant in my oil , the mechanic shop don’t accept responsibility on it 

I change done the intake gasket , I found some rest of the coolant in the heads and inside of the intake . My check engine light turn on again same code p0171 . 
on my truck 2008 LT Silverado 5.3 why I have coolant inside or around the my intake manifold? Run coolant lines around or inside of the intake ? , I just made for second time the gasket replace last night and add stop leak to my coolant system .

what I need do ?? 

 

I’m crazy with it 

thank you 

please help 

Francisco from Pasadena Tx