im guessing it is as my temp gauge went to 130 the other day and was going up and down heaps from like 80 to 110 to 90 up to 130 etc etc so 1st thought was sticky thermostat, replaced it with new 1 and booked it in for coolant flush got that done and its still going up and down heaps in temp and this morning its started to blow white hazzy smoke like coolant burning so i thought head gasket straight away, been rong before though... i bought the car from a member on here (cef11e) with mods done, he gave me a list of mods when i was first talking to him about buying it and there was nothing about head gasket, he just said all new gaskets and seals were used when he built it... (my fault for not asking i guess) so to answer your questions, he did everything he could do himself, im not sure what gasket or studs in it now, its a holset hx35w and it has a remaped ecu that he also tuned himself... its got 175000 on clock and he told me build was done at 140000 so not to many ks since... i mite add this is the 1st real issue its had in the 18/19 months iv owned it!
cheers