I have a big turbo T5 5 speed that developed some surging and intermittant loss of power. The engine has 150,000 miles on it and had an ETM at 75,000 miles and most sensors replaced already. Compression is good and it burns no oil. It spit out codes P1238 and P0236 and P0237. After clearing the codes, it spits out P0237 quickly. After some research I replaced the TCV (solenoid valve) with the proper volvo brand part number 9155936. It didn't fix the problem....the same issue and symptems. I also replaced the fuel filter for yuks. No improvement. I then took the car to the dealer who performed an ETM software upgrade for free (I knew this wouldn't work)and claimed it was fixed. Within 1/2 mile the symptoms returned and the check engine light was back on. Dealer had it another day and then after a few hours of diagnosis says it needs a ....you guessed it...a TCV part number....9155936.
I said....think again, that part is three days old.
I suspect another ETM. The replacement was by the prior owner in 2002. Those things either haven't changed or are still crap.
But....could it be the vaccuum hoses to the TCV? They look pretty good. Any ideas?
The car does not go into limp home mode and the symptoms are intermitant. It does surge and seeming have a lot of power if I get on it.

Help.

Thanks.