I hear the manifold is the best but mine is impossible to get to. I'd like to put it a couple of inches down from the header flange in the mid pipe. Acceptable?
I do not know your application and how far from where the header bolts to the head the EGT will be mounted. Normally it is in the first inch or so. Remember the 1000 +- degree hot will cool some even just a few inches further down the exhaust.
You want it as close to the exhaust port of the head as possible. The 800-1200+ EGT's can cool dramatically just 6 inches or less after where the manifold meets the head. It's going to be tricky to weld a bung or attempt to tap the stock manifold.
Are you installing EGT sensors to tune with, or just to install a gauge?
My next mod will be a Zex 100 shot so I'm going to be running a pillar pod with the pyometer and wide band A/F gauge in it for that little extra safety.
I'm running stock headers and on the right side, I can put my finger into the last cylinder exhaust port on the right bank. So the head is a fingers length away from the flange. I could put it within the first inch of midpipe.
Well, normally people monitor their EGT's for tuning reasons only. If you are wanting to watch the pyro gauge for safety reasons, that unfortunately will not do you much good. By the time you were to see a temperature spike on the gauge, it would already be too late as the damage would have already been done.
The exhaust gases will be way too cool by the time they get to the midpipe to get any kind of accurate reading on the combustion chamber temps. If you really want a pyro gauge, then try to get it as close to the exhaust port as possible.
The other problem is you are reading a mix of 4 cylinder in the header pipe. This can look good yet one cylinder can be lean. If you have the system / manifold run on a dyno with 8 EGT and one in each header pipe to get a baseline then with one in each header pipe you would have some idea of what was going on.
When my friend was checking his N20 hemi on the dyno they used 8 EGTs on one run and 8 Wide bands on the next to monitor the motor.