TCS question regarding power lose...

[lms]

On my 2002 Viggen I have TCS-duh! The car was custom tuned by frank as well. I Have read a little about how it works, but can someone really explain it. Here's the reason I ask.. To start off I love it at times especially in the snow, in super wet road conditions and coming out of corners. BUT, at other times I think it sucks. If I get on it in second and third at times the TCS activates and it feels like the car loses some serious power. If I get on it in 1st, shift fast to second, the car will loose traction, the TCS will immediately activate and the car will almost loose all power until traction come back (bogs down). Also at times when I get on it in second or third I can feel it modulate the power in a big way. It's almost like it's closing the TB a little at times, and other times when the car really lets loose it feels like it's almost closing the TB completely. So when the ecu detects wheel spin, does it shut the TB or am I way off?? Now if I turn it off the frick’n car goes like a bat at out hell. I mean when the roads are dry it's night and day in regards to how fast the car is with it off compared to it being on.
Also, can a tuner adjust the TCS via the ECU?
Thanks