Head gasket fault

[Stockevo51998]

Hi all I have recently fitted E9 80 series 3inch outlet and downpipe to my E5 I have since developed a misfire at around 3000-4500 rpm, also I have noticed that the coolant pipes are all rock hard after a few minutes of driving, do the E5's suffer with head gasket problems as I have noticed that the expansion bottle is empty as well.
Any help would be appreciated I have done a block leak test but found no fault, I know this isn't always accurate so that is why i'm asking.
plugs have been changed and gapped to 0.5, coils and leads also changed

 

[B6lee]

Head gaskets failures are not common except for in the highly modded scene