04 ISX weak jake brake

I just got inframe overhaul done by small shop in IN at 1.4k miles because exhaust gases got into coolant, looks like cracked head since head gasket was still good. Before that jake brake worked fine in all 3 positions. Now 1st and 2nd are still same as before but 3rd position or highest one is kinda weak. Looks like its weakest in top gear which is mine 13th gear. When i hit jake brake it start like 1st position than gets little better but not like before. If i hit it in 12th or lower gears its much stronger but not like before. Mechanic who did overhaul tried swap some kinda jake brake plates that sitts inside head under tho selenoids but still nothing. He said tune up my help when i get back to his shop in 30k miles for readjusting valves but i thing something else is bad
Inframe included full kit, head, injector cups,,connecting rods, EGR cooler, Oil cooler, oil pump,air compressor.
Turbo have about 550k miles on remain one and still runs great 35-40 psi. EGR valve have about 100k miles
There is no codes for jake brake.
So what do you guys think may be

 

Well it was time for tuneup after overhaul. I also bought 2 new engine brake selenoid and wiring harness. Same thing 1st and 2nd engine brake working fine but 3rd one is still weak. And same as before looks like its cutting off on low rpms 1200 od less. Its not straight woshhhhhh. Sound like one of those guys with 10" stacks and wosh wosh wosh just not as loud as 10" stacks. When i was picking up selenoids i talked with cummins service guy and be is saying my turbo isnt working with jake brake because its air operated accuator. If i have one that is electronic than will work together with jake brake. So he is saying if turbo works fine under hard pull with full boost than its not turbo.
How about switch. Or meybe broken jake braks wire outsixe of head, where thkse two wifes goes to. ECU ?

 

Well jake is still the same kinda week on 3 but it may be just fine. What else i found is that when i first use isnt like fusssss. More like fus ssss sssss. Looks like longer i use it it opens up with full noise witbout split second cutting. I think VGT is going bad

 

Well i decided to replace turbo since it started to whine and engine brake got weaker even more. My factory turbo was replaced at 750k due to sticking nozzles but didnt go boom. Reman replacement lasted 780k. This time nozzles started to stick just little bed and shroud plate in turbine housing was cracked.
Engine brake is about 50% stronger, full boost is little higher and pull harder. Not bad for $2500 repair (no labor, i replace by my self)

 

Im still having issues with weak jake brake. Does anyone know where 3 wires from pass throught connector coming from? ECU maybe ? If so what are pins on ECU plug. I wanna check those wires to see if they have good resistance

 

I forget to mention this time switch position #2 and #3 have same performance as #1. Since my original post i replace turbo 2 times, both solenoids, jake brake harness, egr 2 times, 3 times overhead adjustment, 3 front jake brake rockers. Now #2 and #3 is same as #1