I would say, overall, Tren hasn't ever really impeded my cardio outside of painful growth pumps, accompanied perhaps by a sometimes "spicy" tren lung... I think EQ definitely helps endurance and can be beneficial to cardio.
What's very important to note here? The fact that I don't really have any cardio issues after implementing a clean and healthy whole foods based diet plan that includes healthy fruits and vegetables, hydration, and the continued practice of cardio based exercise. It's also much easier to do cardio without toxic doses of orals or mega doses of cheap steroid oils chalk full of dissolvents. I do notice when I pin more during the week, it can definitely reflect on the quality of my breathing being there is a higher level of solvents in my blood - it also causes foggy thoughts. It starts of as light enough of a side effect that it's usually just an indicator for me to speculate and adjust my diet plan and dosing protocols.
I think using a supplement called "afrin" Nasal Spray as well as Aspirin or DayFlu cough syrup (as regular recommended dose) has also helped improve my cardio performance, by helping decongest nasal pathways and provide an effective level of pain tolerance to lactic acid build up. Be careful here with the Acetaminophen, as we are not looking to ignore pains that could lead to injury, but rather manage and tolerate regular pains associated with exercise - like DOMS and Lactic Acid buildup. Also I think electrolyte and mineral intake is very important when considering muscular strength, endurance, and performance.