I am driving a nissan model that uses the pre 94 GA16 engine. Recently, I went for a full rebuild and the mech did a high compression using dome pistons from another car. Ever since the rebuild, I would experience a rattling sound when the engine is warm and especially when I rev from 2500 to 4000rpm. In addition, it would sometimes start to emit bluish smoke when the rpm is in this region. When this happens, there is also a strange odour in the cabin. I have tried adding a aftermarket piggy back ECU and changing the timings and fuel supply but the problem still persists. Really confused and helpless. Please help!!!!