The only way ECU can raise idle speed is via the ISCV, they can cause problems with sticking which could cause your problem, so unplug to eliminate. The standard chip with a 3 BAR MAP sensor will make it run rough as the output is totally different to the standard 2 BAR. If not ISCV then presuming you have the base idle set right will be an air leak. You also need sutiable injectors for the new chip and hopefully have a decent HG.

Martin