Throttlebody MAP Reference
 

After adding BOP's to my manifolds I had a hard time starting due to using the throttlebody's input for the vacuum/boost. I have been running lately with it hooked up to the UIM instead sense I'm getting a good source there. What would the reason for the throttlebody's vacuum/boost reference not be working correctly? Anyone else have have similar issues. Am I going to cause harm using a source farther down the intake track.

Thanks

I also went sequential at the same time I had MAP problems. Could the opening of the secondary throttlebody's be causing it to not see enough vacuum.