I'm all out of ideas on what to check next. 90 sohc 240sx. What its doing is, get the car up to about 80 mph the car shuts down, falls flat on its face like the gas was turned off. The car shuts down. Don't know how else to describe it. ALWAYS around the same MPH. I have replaced the following:

ECU
Injectors
FPR
MAF
TPS sensor
Fuel Pump
New cap, rotor, plugs and wires

Any idea what I should check next? He is about to take it to S&R to have them fix the problem. By the way, except for exhaust, the car is stock.
Thanks.....