MassNorth

I have a 2004 FX4 5.4 v8, the only real upgrade is dual flowmasters. Two months ago I had the manifolds and the y-pipe (aftermarket not Ford stock) to the kats replaced (the truck was sitting for over a year and they were rotting). It runs absolutly great, defiantly night and day and it is like it is brand new again. The only thing is the check engine light goes on for a couple days, off for a week, on for a few days, off for week, etc. Now the last few days (with the check engine light off) I have noticed a very light squeak. It is more of a ticking pattern in the squeak opposed to a constant squeak. It seems to only happen at low speeds and when the truck is started cold (I live in New England) after it warms up it appears to dissappear. I am wondering if this is an early sign that the mainfold issue was not completly solved and could use some more work, or if this is something else (belt, etc.) Or if this is something to be concerened about. Thank you guys.