7mg(t)e's are notorious for blowing headgaskets. Most of the time at the back of the head and leaking coolant externally. personally i wouldnt turn up the boost much unless you are prepared to replace the HG. i have in the past torqued the HG down more than the OEM specs and never had a problem with 14psi...but the engine only had 70K on it and was babied from the start. other than that its a fairly strong engine.