It depends on the severity of the leak. For me, it started out only pushing gasses in under high boost and high engine loads. Day to day driving around town I never had issues. My coolant system would vacuum the coolant back in if I let it sit overnight after a problem occurred. As it went along it started happening more frequently and finally had a compression test, wherein I found out about the ring seals (60 PSI in #4 = no bueno). Get a compression test. If you do have HG issues solve them ASAP before you cause any further damage, new motors are not cheap.