Overboosting / Timing Pull at 10 PSI - Faulty Manual Boost Controller

Turbobeginner✓ OP Confirmed

Problem

7MGTE with forged internals and CT26 (48 trim) was overboosting and pulling timing at 10 PSI. The engine appeared to retard timing under boost rather than hitting fuel cut cleanly.

Timing retard/pull under boost at 10 PSIOverboostingMiss at idle that cleared up at higher RPMs

Root Cause

The manual boost controller (MBC) was interfering with the wastegate signal, causing the wastegate to not regulate boost properly, resulting in overboosting and the ECU pulling timing as a protective measure.

Confidence

Moderate confidence — Original poster confirmed this resolved the issue

View Original Thread →Posted October 2025 on SupraForums.com