We have investigated a new type of a so called "modified PVT setup" with an additional gas flow into the growth cell. The motivation was an improvement of the parameter control for doping of SiC using gas sources, i.e. homogenization of doping levels. Since an additional gas flow inside the growth cell could cause severe distortions of the vapor flow we have performed basic investigations of the influence of an inner argon gas stream on thermal field and structural properties of the growing crystal. We have studied the impact of the extern gas flow towards the surface of the growing crystal. Strong evidence for micropipe closing in the initial growth stage and reduction of second phase inclusions was found.