Does $\Lambda$CDM really be in tension with the Hubble diagram data?
  In this article, we elaborate further on the $\Lambda$CDM "tension",
suggested recently by the authors \cite{Lusso:2019akb,Risaliti:2018reu}. We
combine Supernovae type Ia (SNIa) with quasars (QSO) and Gamma Ray Bursts (GRB)
data in order to reconstruct a model independent Hubble diagram to as high
redshifts as possible. Specifically, in the case of either SNIa or SNIa/QSO
data, we find that current values of the cosmokinetic parameters extracted from
the Gaussian process are consistent with those of $\Lambda$CDM. Including GRBs,
in the analysis, we find a tension, which however is not as significant as that
mentioned in \cite{Lusso:2019akb, Risaliti:2018reu}. Finally, we argue that the
choice of the kernel function used in extracting the luminosity distance might
affect the amount of tension.
