I don't think the 3.0 manifold will fit under the 190 hood, and I also think it has slightly smaller ports, which will limit top end power... not sure about the exhaust manifold ports.

...suggest you use a dial back timing light to map out the WOT spark advance curve with the vacuum line to the EZL disconnected and plugged. The 4000 rev torque surge may be caused by a lazy spark advance curve below that speed.

Duke