P0441 Code on 97 Monte Carlo, Please HELP

I purchased a used 97 Monte Carlo Z34 with the 3.4 DOHCand am having trouble with the Evaporative Control System. The car has 145K miles and was running great when parked for 1 year. I purchased it and now I'm getting a service engine soon light whenever the car is started and driven without letting it warm up first. In other words if you let the engine warm to operating temp then drive off you get no code set reguardless of how far you drive. However if you just crank it and drive off within 5 miles the P0441 code is set. I purchased a Haynes Manual and they must think everyone is dumb because they just say to see your great GM dealer if you have problems. I cannot find a good diagram of this system. I do not have any special tools but have searched for vacuum leaks, hoses off and things like that. I have connected a vacuum gage to the system and have 17" prior to the 1st valve on the engine and when it opens I have 17" vacuum to the second valve on the engine but the vacuum after the second valve is only 5" and pulses. Any help with this problem will be greatly appreciated. Even with the Service Engine Soon light on the car drives and runs great. Thanks for any Help

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