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Hey guys. I've been having this issue for a while now and decided to post up. I have a s13 sr20det in my Datsun that I've been getting dyno tuned for a while. The issue is the the engine isn't holding boost. It will boost up set pressure but would taper off. My tuner and I have boost leak tested this engine and have seen leaks before which we all fixed but now there are none. The engine has a gtx2860 gen 2 internal wastegate with hks actuator, greddy manifold and Tomei poncams. We tested on wastegate pressure only and it would spike to 14 before dropping down to 10 which should be the spring pressure. Very strange for the initial spike in pressure to 14 before dropping off. What areas are common for the boost to drop off to?

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lexus baby