Emissions going out from the cloaked vessels should reveal it.
Emissions directed to the cloaked ships should reveal it(As a remedy, I say, no heals from allies while cloaked)
Anything done that remains within the cloak field should not reveal it...by definition, the cloak is designed to keep emissions inside and non-detectable by sensors outside the cloak field...so self heals should not cause detection.
The power required to run the cloak doesnt change, its still being directed from the shield systems...so there is no reason for the cloak to drop. Think about it, the cloak in canon didnt drop due to power drop offs when Chang fired the torpedo. The B'rel became visible because the torpedo broke and disrupted the cloak field as it passed through. The whole B'rel wasn't seen because the claok field never dropped, it was the ambient light being thrown off the torp that was illuminating the front of the hull, while the distortion in the cloak field allowed that light to pass out and be seen.
The B'rel's cloak was "perfect", it was never lost or dropped...the probelm was that they couldnt adapt to the distrortion of the weapon firing through it, nor did they have the surplus power to fire a beam weapon. the B'rel was detected becsuse it was emitting a non-energy waste product. The Cloak manipulates energy emisisons for sure...exhaust gases/ions are matter, the cloak(s) wasn't manipulating matter emissions...at least not those. Either the disigners didnt know it was getting out(because they had already learned to contain them), or didnt expect anyone to look for it...because apparently it took heavy modifications to even have a chance at detecting them....somethig no ship of the time had...and apparently no ship of this time has now, because exhaust emissions have never been used to detect cloaked vessels again since then.