That's 320 naturally aspirated with stock fuel pressure. With the NOS you are ramping up the pressure just for the hit. Then it's back to normal. 125/150 is the limit for the stock injectors. Anything over that with the stock injectors then Kaboom!
The whistle is most likely a leak in the upper intake. You said you took it off. I'll bet that is it. You need to retorque the upper manifold between 20-24 ft. lbs. If that does not work change the gasket and torque down again.
How come the Mach 1 engine is only $3000 brand new and the older Cobra engine is $5000 brand new? $2000 is a big difference. I thought the Mach 1 block was a little more powerful.
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My car runs without 02sensors just fine. Some guys disconnect them at the track to get more power. The 02sensors are there for emissions purposes.