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Discussion Starter · #1 ·
I replaced the stock all plastic NPI intake with an aftermarket NPI intake a few weeks ago. I have noticed that I have lost approx. 4mpg highway! I double checked all vacuum lines and everything else that I could think of checking. Are these aftermarket intakes made differently than the stock OEM types?

Thanks
 

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Double check for a vacuum leak somewhere. If you take a can of carb cleaner and start spraying it around the intake, the motor will rev up a bit if you spray it where there's a vacuum leak. Maybe you knocked one of the gaskets off a bit and it isn't sealing or something like that.

Mike
 

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Egr?
 

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try checking to see what your idle vacum is at, if you lost 4mpg, it happened from something being disturbed doing the swap

and ya a clogged EGR would cause miledge to go down, as egr cant flow when your cruising to increase your mpg, but its probably unlikely swaping an intake manifold would cause it to become clogged

maybe you had brittle vacum lines and moving stuff around cuased one to hairline crack causing a leak?
 

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Discussion Starter · #5 ·
The engine runs great and it seems like it is a little more peppy after the swap. I think that I am going to replace the rigid vacuum lines with rubber ones. How do I check the EGR to make sure it's okay? BTW, I did clean the MAF!!
 

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remember, the egr needs the dpfe to be hooked up. is it? it also needs the EGR vacuum regulator solenoid hooked up electrically, and seeing vacuum. is it? if you can eliminate these components from the list and it still persists, then you're one step closer to finding the problem
 

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try to clear the computer too by removing the fuse under the hood, then try to start it, replace the fuse, start it and let it run for 5 min, then drive it throughout the gears. it might help
 
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