Hey guys, I have an 05 5.4 3v with a leveling kit, 35s, k&n CIA, and bullydog programmer and I have been having a problem with its acceleration. Whenever you take off wether it's from a stop or while changing speeds such as getting on the highway it makes a loud vaccum noise and struggles to get up to speed. I thought it may have something to do with a bad MAF sensor but I really have no idea. Any advice is appreciated.

 

A loud vacuum noise sounds to me like a bad fan clutch.

 

You could try cleaning your MAF with MAF cleaner to see if that's what it is, maybe your TPS but it's hard to tell without actually driving it

 

I cleaned my MAF but it didn't do anything, would it be throwing a code it it was bad?

 

Also a loud vacuum noise or bog down noise can be the foam around the air filter drawer is gone or deteriorated. Thats the sound that I got when i had that issue, changed the foam out with new weatherstripping from home depot, about $3.00 and good to go since.

 

He said he had a CAI installed....

 

Describes my problem exactly. I'm going to say its a bad catalytic converter.
With a cold engine, take it for a two minute drive. If the converters are different temperatures then thats where I would start. You could also unbolt the pipes at the manifold to do a test run to check for improvements.
https://www.f150forum.com/f4/06-5-4-...-fires-291476/

 

If its a bad cat(s), Dont put factory cats back on because all they do is limit your engine, decrease fuel economy and eventually clog themselves.

 

lol...