hi guys. first of all im new. my name is marcel and im from southern california.

im having an issue with my truck and coming here to ask for suggestions.
i have a 2007(classic) silverado with the 4.8L
my computer is tuned(hp tuners) to run off a speed density tune.
fuel system is not stock. aeromotive pumps and filters and FPR (all confirmed in working order.) no evap components.
everything has been the same for a little over a year with 0 issues

the problem:
i got a CEL for a bad knock sensor. replaced it and thats when my problems started.
when i start the truck cold it starts and runs PERFECTLY fine. no problems at all.
when the truck is at operating temps or near them and i start it the idle will immediately rise to about 2000 then drop to a somewhat lumpy idle. sometimes after putting in gear itll drop very low into the rpm range around 200-300. again these problems only happen when the engine is warmed up


things iv changed:
new intake gaskets
throttle body gasket
coolant temp sensor
smoke tested the intake (when the engine was cold) with 0 noticeable leaks


any body have any idea as to why this is happening? are there certain vacuum lines that are activated when the motor is running closed loop rather than open loop or vice versa? would an 02 sensor cause things like this?

thanks for the help. cheers

 

no one has any ideas?

 

First thing that comes to mind would be the EGR.