P0171 code has me stumped

I have a 2006 2.7 prerunner that I installed a new heater hose pipe on the other day. To do this I had to remove the intake manifold and throttle body. While I had the throttle body off I cleaned the carbon build up out of it. When I out it back together with new intake gaskets and and throttle body gaskets it will throw a code p0171 bank 1 too lean. It throws the code about 5 -8 minutes after startup. If I clear the code while the engine is warm it doesn't throw the code even after driving for 30-45 minutes. I also have a non oiled stock type air filter. Also the spark plugs have 1k miles as I just changed them month ago. Truck has 155k and did not have a check engine light on before I changed the hose or anytime in the last 8 years I've owned it.
I tried spraying starter fluid around everything to see if it had a vacuum leak and it didn't rev up like it would if it did.
Also the truck makes a pssssssss noise when I shut if off. It didnt do that or I didn't notice it before. My dad has the same truck as mine(2.7 5mt) except it's a 09 it doesn't make that noise either.

 

Pssss noise sounds like you might have air in the heater system

 

Your noise might indicate a pressurized leak, the opposite of a vacuum you looked for.

Maybe recheck all the recent work. Even if all hoses are reattached make sure none have split ends. A little soapy water in a spay bottle might show some bubbles of a leak.

Try to zero in on finding the source of the sound. I bet it is related to the issue.

 

I left a vacuum line off the very back of the intake manifold when I put it back together.