Overfueling by me? or too much fuel going in?
I do get a wooshing kind of noise like if the car is doing an impression of K.I.T.T from Knight Rider.
The car does feel down on power, and sometimes when I accelerate I do not move too quick until the rev counter does to 2-3 revs from a 1st gear start.
When I am in 4th and I accelerate to 40 it takes a second or two longer and the black smoke comes out.
Too much fuel (or too little air) going into the cylinder, causing incomplete combustion and a load of smoke as a by-product.
Whooshing noises, smoke out the back, down on power, laggy response at low revs.. All indicate boost leak and/or VNT issues... Easy fix in either case!
Take a look under the bonnet, the big hose on the right that goes over the battery - any holes or splits in this?
There's another big hose down low behind the bumper - this one fails more commonly but is harder to see without lifting the car on a jack or with wheel ramps.
VNT issues are often due to split/leaks in the vacuum hoses around the VNT actuator and solenoid - again a nice simple fix if you find an issue here.
As far as timing belt and water-pump goes - they should both be replaced (along with a belt tensioner, and idler pulley) every 60k miles OR 5 years - whichever is soonest.
Do you know if/when your car has had one in the past? If you've got no record of it every being done, then yes it needs doing ASAFP.