If you run the TRS for PCT properly, you should keep every bit of your gains from a Turinabol LV/Halodrol cycle (most people can attest to this).
You have to keep calories high during PCT regardless (or your body will burn that new muscle instead of old fat for energy) and then titrate to your new BMR (basal metabolic rate). If you put on 5 lean lbs for instance, your calories needed per day will increase to sustain your new weight.
During PCT itself, it is usually best to err on the side of eating a bit too much rather than too little-you just don't want to give your body a chance to rid itself of that unwanted new muscle (that is the way the body sees it). And then just do cardio+adjust diet or whatever you do to reduce fat (stims, etc) say 2 months down the road after your weight is solid and you can cut any fat you put on during PCT and still keep the muscle you gained. Once your new weight solidifies, it becomes like your old weight-the body wants it to stay the same (a good thing if you do the above correctly). Just DON'T go on a diet during PCT-that is the easiest way to lose all your gains.
BTW, I've kept all of my gains for my last 2 cycles (and I gained a few lbs of fat too, but nothing I can't get rid of). When I first started doing cycles several years ago, I'd gain a lot and lose half because I didn't know much about PCT and I was using highly suppressive compounds like M1T. Turinabol LV is not highly suppressive by any means.
So the short answer is yes, you can keep your gains; just use a solid PCT like the TRS and follow some PCT diet guidelines and you will be good to go.
