Headers with no EFE

Ok here we go :)

I own a 1990 chevy G20 TBI 5.7 Van Full size
about 2 years ago i got headers put on the van not knowing much about it a freind reccomended hedman headers. so basically ever since i got these headers it has been running on and off badly. mostly bad in the cold weather warm weather its fine.

im by no means a mechanic but i got the haynes manual for small jobs and things that are easily done to save a few bucks.
I took of the doghouse the other day and in there on the left side was my headers etc i noticed that the EFE was not even there the mechanic removed it and didnt say anything about it to me.
(this guys did plenty of other shady stuff he is no longer shall we say my mechianic)
so now i dont know what to do i since have tried to compensate for my
-rough idle
-occasional surging
-abrupt jump foward when placing it into gear
-horrible idle control and stalling at low speeds

are hedmans bad headers that are causing this problem?
go i need to get a heated o2 sensor?
can an efe be installed after the headers are mounted? like i mentioned its gone! along with any vacuum hoses went with it


thanks alot