Ok I am not super familiar with valve train issues. Ever since I have had my turbo engine in my Z it has made lifter noise (loud and obvious ticking) sometimes right after starting if it has been sitting for a long while. It used to go away and was no big deal. Well now it is making a less obvious ticking noise while driving, usually for only the first 10 minutes or so of driving, and is only really audible under load. If I gun it and get on boost, it makes a terrible squeeling noise, as if air from the turbo is leaking out somewhere or something. As soon as the ticking noise goes away, everything is back to normal. No squeeling noise, just normal boost noises. Of course this is all after trying non synthetic oil for the first time in the engine (since I have owned it anyhow) not sure if the two are related. Any ideas?