I had it taken to a shop and thats where they installed it, I thought they knew what they were talking about??
Either you misunderstood, or else you have an idiot for a gauge installer.
A thermocouple (sender for a pyrometer or EGT gauge) in the downpipe (which is post turbo) is used only
for engine shutdown. It is NOT
used for driving. Lots of OTR trucks have a post-turbo pyrometer, but it is used only to tell the driver when it's okay to turn off the key and shut down a hot engine/turbo. The computer program (tune) for the engine prevents too-high EGT when driving.
The computer program that controls your stock engine also won't pump enough fuel to cause too-high EGT. So Ford doesn't provide you with a stock pyrometer. But for driving with a hot-rod tune, you want the thermocouple mounted before the turbo (pre-turbo), either in the exhaust manifold or in the up pipe between the exhaust manifold and the turbo.
Out here in cow country, we have lots of "cowboys" driving hot-rod Pete 18-wheeler cattle haulers. But along with their hot-rod tune, those "good ole boys" all add a pre-turbo pyrometer for driving, because they know their stock post-turbo pyrometer is only for shutting down a hot engine. And if you think a holed piston in your 7.3L engine would be expensive, have you priced a 15-liter Cat lately?
I know not to pass 1250* from the downpipe, but what should they not exceed if tapped into the manifold?
As others have mentioned, you were misinformed. The 1,250° red line is with a pre-turbo pyrometer. Nobody knows the red line with a post-turbo pyrometer, because it varies so much, affected by several conditions. I've seen my pre-turbo pyrometer over the 1,250° red line while the post-turbo pyrometer was still back at 850°. I've also seen my pre-turbo pyrometer over the red line and at the same time the post-turbo pyrometer was sitting on 1,200°. So what is my post-turbo redline? If I have only one pyrometer, and that one is plumbed after the turbo, then I'd use 850°. Others have said 800° would be safer.
The purpose of a pre-turbo pyrometer is to protect the aluminum pistons from meltdown caused by too-high engine heat. 1,250° EGT is the red line because the melting point of your aluminum alloy pistons is a hair more than 1,250°.
The purpose of a post-turbo pyrometer is to protect the turbo from disastrous high residual heat in the turbo bearings when a hot engine is shut down. Most automotive engineers agree that about 300° to 350° is the maximum shutdown temp, depending on your motor oil. Since I use dino motor oil, I use 300° as my shut-down temp. Synthetic motor oil is not cost effective, so I don't waste my money. But one advantage synthetic has is it can stand a bit more heat without deteriorating. So if you have synthetic motor oil, you can shut down at around 350° EGT.
I have an automagic gizmo that shuts down my engine when the EGT cools off to about 300º. In the meantime, I have the keys in my pocket, the doors locked, the steering wheel and tranny locked, and I'm going on about my business. The gizmo is an ISSPRO Turbo Temp Monitor (TTM), available from any ISSPRO gauge dealer. With my TTM, I don't need a post-turbo pyrometer to tell me when it's safe to shut down the engine.