We investigate the interplay between ion temperature gradient (ITG) and parallel velocity (PVG) instabilities in cylindrical geometry using a Water-bag model 5D gyrokinetic simulations with modified version of GYSELA code. The provides an analytical dispersion relation, which is compared to linear simulations. Strong agreement found predicted simulated growth rates real frequencies, validating GYSELA’s applicability systems. comparison also highlights key parametric dependencies on instability thresholds, including effects density profiles, gradients, shear. Notably, weak gradients are stabilize PVG modes, whereas strong tend destabilize them. Additionally, flow shear shown enhance ITG-PVG hybrid modes. These properties likely impact turbulent regime.