Engine missfires at low rpm and shakes . Code said #4 not firing vacuum leak

What is your question?

I changed map sencer, fuel filter,and coil pack Nothing worked. Tried copper seal in case of cracked intake still didn't work. Drove it and it runs fine at high rpm but misses at low rpm.

What makes this problem better or worse?

Runs worse when cold

How long has your 2001 Oldsmobile Alero had this problem?

Couple days