TDV6 inlet manifold leaks

[Escape]

A while ago I had a TDV6 come in that was low on power unless revved hard. I found codes for the EGR and as they had done almost 200k miles decided to replace the valves. It turned out one was instead stuck open. However, before the new parts arrived, a new problem develloped: lack of power when pushed and a lot of black smoke. When I replaced the EGR valves, I also found a leak in the throttle body. It looked like something had melted through from the inside. I tried a temporary fix with JB weld, that seemed to hold but the next day 2 new leaks appeared in the housing. I put it down to the plastic being weakend by the EGR sticking open and replaced the housing. All well for a testdrive, then another leak, this time in the LH inlet manifold. Again it looks like something burned through. The EGR valves being new, should do their job. Exhaust gas coolers seemed OK, no visual leaks. There is a reasonable amount of oil in the intake, which I put down to the mileage.

Before replacing the manifold, I'd like some opinions on a possible cause. I don't want to just throw parts at the problem until it goes away...

FYI, the car is a 2008 RRS, but I decided to post here because there seems to be more knowledge about the engine in the D3 and I didn't want to exclude anyone.

Filip

[reb78]

Its the EGR I think as you say. This is documented with the D3 - valve sticks open and it runs on hot exhaust gases only. You have already fixed the cause.

Edited October 28, 2019 by reb78

[Escape]

I'm hoping it is indeed the EGRs. Just strange that the problem seems to have become worse (i.e. new leaks occured) after the EGRs were replaced.

[reb78]

I am no expert, but i suspect the plastic will have become brittle and perhaps the improved airflow due to the EGRs closing properly has found the weak spots?