2006 gmc savana 2500 misfire got worse after i replaced spark plugs and wires

What is your question?

I was informed to replace plugs and wires after bring vehicle to garage. Vehicle was already misfiring after replacing plugs and wires car was worse set plugs to .040 on the gap as instructed what can I do to fix issue

What makes this problem better or worse?

Worse when changed old plugs and wires

How long has your 2006 GMC Savana 2500 had this problem?

Few weeks