Going on high doses of tren ace will do the same thing. It's pretty common that tren will leave you with less aerobic endurance. I notice it most when I'm doing squats. What you have to remember when going the tren e route is its half life of 7-10 days and how much and how fast levels will build up in the blood. If I remember, Chris250 was doing a high dosage of tren e over a long period, 300-400mg, and that was what caused his heart problems.
Take 300 mg of tren ace at a half life of 2 days over one week (Feel free to correct me if I'm figuring it wrong)
M T W TH F S SU
100 100 100 100
-50 -50 -50
-25 -25
-12
TOTAL LEVEL AFTER ONE WEEK
100 150 175 188
300 mg of tren enanthate at a half life of 7 days over one week
M T W TH F S SU M
300 300
-150
TOTAL LEVEL AFTER ONE WEEK
300 450
As you can see, as you keep going, tren e goes really high really fast. By the next week, you would have approximately 525mg still in the blood. You don't need anywhere that kind of dosage to get the same benefits as when using tren ace. Not to say that you can't use tren e safely, because you can. You just don't need as much of it as you think.