Hi guys, I know I asked you guys before and the loud noise went away mysteriously for no reason but again, it comes back again. Here is what happened. I discovered that the loud noise comming from the engine return every time I allow the RPM up to 5000. and as soon as I parked the car for awhile the noise went away. Could it be low oil pressure?? because the rpm drop to zero and then back up to 2000rpm, this keep happening all the times. I only have this problem in the winter(first time in winter after swap) could it be because of the cold weather? while the rpm drop down to zero, the motor didnt die or stall, but the motor shakes and tilted and rocks like its going to die and then when the rpm went back up to 2000rpm like someone stepping on the gas pedal, the motor runs smooth. the noise sound like I have something loose in the engine. could it be that i have a FLOAT SPRING(S) since i used to shift hard at 8500RPM with stock gsr camshaft, valve trains? just for info so that you guys could help me firgure out what's wrong with my car. the motor has no leaks of oil or coolant anywhere, no unusual smoge from the exhaust,the motor is clean.