454 Magnum temp Gauge going up but infared gun shows normal

Please Help!! I have a 1987 454 Magnum with an Alpha Drive and she ran fine last year but this year its been heating up to over 200 until I go back to idle and it slowly comes down. The alarm has never sounded and when I put a temp gun on it the temp shows 160. I have replaced the thermostat and the temp sensor. I have replaced the gauge and it was the same, I pulled the bottom hose coming from outdrive water pump and the water flow was 6 inches and when I revved it up it came out even further. The impeller is two years old with no shallow water running at all. I even tried running a separate wire directly from the sending unit to the gauge and its still the same. The only thing I did different this year was I added two 400 watt amps to my radio, I even tried taking those off the batteries and it was still the same. One of the hoses is very soft, not sure if that is anything but any suggestions would be very welcome. Thanks to all