Firstly, you say it Runs 10psi with DV fitted but 27psi without. Id say the DV is knackered, spring or vaccum not sealing under boost.

Second of all, You mention it ran a t3 on dyno sheet but now has t34.
Id say the misfire is unrelated to the DV and could be down to the chip not being setup for the T34??. Ecu is detecting overboost and cutting the amal valve in hence the misfire etc. Sounds plausable. If this is the case, you have two different issues, the latter could cause serious engine damage.

Personally, if you not 100% sure of the current map setup etc, id pay the money and have a new chip done for the current setup by someone like MSD.