Hmm...first of all, your intercooler is fine. Supras with that dimension IC made over 900rwhp. I'd check for leaks and do a compression test. Also, you said you ran 1.7bar. Did your boost gauge read that? It's also possible that your 9psi wastegate springs are too soft. If your boost gauge has play back, I'd check to see if boost held at 1.7bar or just spikes.