Looked at mine today, troubleshooting an over-heating issue and reminded myself how ridiculously small the turbos are on these trucks.
Solutions (which you think the engineers at Mitsu would know, as they have been building trucks for a few years now)
Properly sized turbo keeps EGT down, compound twins do an even better job, Additionally, there is no turbo lag.
Large amounts of back-pressure are not ideal in a turbo diesel application.
Replacing the traditional EGR system with any one of several alternatives, prevents hot exhaust gases from being introduced back into the system.
"typically" OEM intake and exhaust systems are designed for price points, emission, dB and/or NVH levels, etc. They are NOT designed for optimum performance, top notch quality, ease of service, maximum flow, etc.
With this engine being mostly electronic, I presume that tuning it to compensate for your changes will be a nightmare. It would be nice to have a small part of the aftermarket tuning options/accessories that domestic diesel trucks have in the US.
A TD-04 turbo is quite common in the import car world. You may have some luck swapping parts there or getting one built to improve your performance.
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