Volvo Repair: ETS, maf sensor, oxygen sensors

Question
I have a 1999 V70XC with 91,000 mile on it. Black smoke was coming from the exhaust, then the smoke wnet away. Few days later the ETS light came on for few minutes then went away. The black smoke and shaking at the light came. Took the car to the dealer, and they replaced the ETM. Drove home from the dealership, the smoke and the shaking returned. Took it back to the dealer, and he replaced the MAF and the smoke returned. Dealer told me that i may need O2 sensors, had the front one replaced with no luck. Took it to local mechanic and he told me that the inlet tube to the turbo is leaking and the turban seal may have to be replaced. Taking the car back to the dealer for the seal replacement. Will this help or just wasting more money. Spent $2000 already. HelllllllllllllP. vijay

Answer
Hello,
Firstly, I should say taht the local mechanic is true, leakage for turbo problem has to be solved.
However, at the other side the dealer is true, too. The oxygen sensorS should be replaced with new oneS. I am speaking PLURAL, they spoke SINGULAR I think. So for this case, they are WRONG. Because, according to your writings there was black SMOKE. It means that there was problem about emission system, also ETS light came, it says same thing. Emission system is a combined system that works together as inlet and exhaust side. At the inlet side, the MAF sensor and ETM and at the exhasut side there are oxygen sensors. If one of them has faulty, the other ones are affected because of that part. At your problem, firstly the ETM had problem, but I think the car drove more with this problem, because of this reason there was black smoke, so firstly, oxygen sensors were affected, and after that the MAF sensor lost its calibration. MAF sensor is very "sensitive" part, it works with "hot wire anomemeter" principal, its technology is very high, very high-tech part, because of this reason it is expensive. It is produced by Bosch.
Briefly, get the turbo leakage problem solved, and get the oxygen SENSORS replaced with new one. The dealer will say you there is a faulty code for front oxygen sensor, but they should "comment" about it, front & rear oxygen sensors are defective now, especially because of black smoke problem. Also, ask them, there are Software Upgrades for ETM (Part Number 30677007) and Engine Control Module (Part Number 30677005), if they Upgrade these Softwares it will be very beneficial for your car. The softwares are cheap, both of them is approximately only one USD. (1 USD)
Regards...