Timing Not Advancing

[nickapaso]

Hi everyone. Newbie here. My name is Nick. I bought an '88 Supra turbo 5sp. the other day. It has a new motor with about 1000 miles on a freshly rebuilt motor. I drove it about 200 mile in the last two day and it ran great. Then when i was coming home last night it started spttering badly when boost would build. I mean it wouldn't even rev above 3k. It revs fine below that, but once boost builds it just sputters and drop below the boost range again. So I limped it home and chacked all the lines and wired and found nothing out of the ordinary. I don't have any boost leaks. I think it is a timing related issue. It idles fine and is running on all cylinders It is an 88 supra with a greddy td0620g turbo with a boost controller and a turbo timer. It has a greddy front mount and a stillen fuel pressure regulator and greddy bov. I was only running .4 bars of boost for the break in.