code 1406 and 0153 (1997 5.7)
 

To make a long story short i get a code p1406.. i replaced the egr valve and it dont correct my problem.The motor runs a little rough on idle,i replaced the egr and no change in the idle.This problem only started after i fixed the intake manifold gasket!! now it idles rough (but it runs great going down the road) and now i got a code p0153 with the p1406!!! Can anybody point me in the right direction..thx for any input!!!

You said the problem started after you fixed the intake gasket. Sounds like a vacuum leak. I found this on another site about the P0153.
A code P0153 may mean that one or more of the following has happened:

The oxygen sensor is faulty
The wiring to the sensor is broken / frayed
There is an exhaust leak

Good point old chevy..lets talk about a possible vaccum leaks.On this 5.7 l motor there arnt really any vaccum hose to leak.. You got the big hose that goes from the power brake boost, and then you have a hard plastic line that runs from the black canister(near the radiator) to a device on left side of the intake manifold.Thats all i can come up with for a possible vaccum leak,if you know where more possibilities are at please let me know.And to let you know ,I did have it timed correctly but do you think the code 0153 can make idle rough??