Recently overheated 300CE due to bad water pump. Had pump and tensioner replaced, and immediately upon driving out of shop, the car has a misfire and sounds like a boat. There is also still an overheat issue with no water leak. What can this possibly be?

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Turboman

1993 300CE Garnet Red
Eibach Springs
18x8.5 ADR M-Sport wheels (Hyper Silver)
Metal Master brake pads
Semi-gloss black front grill insert