I’m not sure if anyone has the exact weight for the viper because that may change the calculations, currently I’ve assumed a weight of 16.5 tons.
But going with that educated guess, I would say it should have no trouble keeping up with older tanks like the Al-Zarrar, the type 85UGs and the T80UDs. It will probably also be fine following Al-Khalids, but will likely not be able to keep up with VT-4Ps, another thing to take into consideration would be the future plans for the Al-Khalid, which do include a more powerful engine, maybe the same one from VT-4 or a Ukrainian option.
However that also reminds me that there was a more powerful engine option available for the Saad APC itself, 405 HP I believe, I wonder if that has been or will be considered for the Viper, it could boost the mobility. But that still does leave some questions about it’s protection, if the base protection is STANAG level 4, then it should be able to stop 14.5MM rounds, and with Cage armor or ERA, maybe RPGs as well, how that would effect mobility also remains to be seen. I also remember you asking about how the aluminum armor of M113 (flammable) would react to getting hit given the M113s being battle taxis aren’t supposed to get hit, but this thing will. I assume the add-on armor isn’t aluminum at all, it is very likely steel, and I recall that Pakistani M113s/Talhas/Saads have their fuel tanks moved to reduce the risk of fire as well. The engines found in the Newer M113 models are also far less likely to catch fire than the original M113s.
Keep in mind the armor, weight etc are my speculations but are hopefully close to the realistic values, I’d also wait and see what the new version of the viper is like, considering that it does seem to be somewhat modified from the original. PA may have asked for entirely different specifications.