Engine tuning is something that you may have considered. Regarding the A16LET engine, BSR has no tuning kit yet available, but some other companies do.
The big question though, is up to what point the reliability is not affected. MGI Motorsport claims that the "Opel / Vauxhall 1.6 lt turbocharged series operate with safety up to 205 Hp and 27 Kgm because of the design and the material of the connecting rods, which is weak for higher performance".
I found also a very good link with information on Opel turbo engines, but it is in German. Check it out!
