Q: just had my steering rack replaced. My fluid is full but now it's tough to turn wheel. and white smoke coming from under the hood.

This suggests your power steering pump may be failing or you have a leak elsewhere in one of the power steering lines. The power steering system operates on very high pressurized hydraulic pressure (in some cases as much as 300 psi). As a result, the pump works very hard to maintain the ability to assist turning your steering wheel and when the pump is overworked due to the rack and pinion not pump fluid properly or potentially due to pinched fluid lines, this may cause it to leak. When this happens, as the pump loses fluid it may cause it to squeal or whine as a result of inadequate fluid. The lack of fluid will cause the hydraulic pressure in the system to drop and you may notice the steering becoming a bit more stiff when turning the wheel. Power steering leaks are fairly common, but should be looked at immediately by a qualified mechanic as power steering fluid can be flammable especially when under extreme pressure. I would recommend having an expert from YourMechanic come to your location to diagnose your power steering system.