The readings should be the same between the boost bolt and tapping the plate.
The OBDII port should give you the same readings, as it's reading from the MAP sensor which is also mounted on the intake horn. I decided to just tap the plate and be done with it. Also If and when I get around to cleaning my intake horn I can just unbolt the plate from the horn instead of messing with the boost line and fittings.
Plans, well....
After swapping the turbo out the stock 3 bar MAP wouldn't read high enough so I started looking into gauges...starting with the boost gauge.
I had been wanting to switch to EFI-Live but didn't want to lose the OD tuning. I came across a really good deal that I couldn't pass up for EFI-live and a tuned TCM so I jumped on it. I actually just sold and shipped out the MM earlier today.
I've have the EFI-live for about a week, and I love it...It's a world of difference. We are still working on the tunes, but what I have thus far is awesome. I HATE how the 68RFE shifts stock so I am shipping my TCM to him Monday to have that tuned.
It's a trickle down effect, It looks like a higher flowing intake is next up.
Might be selling my MP8 soon if anyone would be interested.