Speak of the devil...not bad with that SS Trueno 725, espcially on midfield, you obviousy still have some things to learn (who dosen''t? myself included) but you're doing good I suppose. I say speak of the devil becuase yesterday I was doing some drift pratices with my Corvette Z06 on that said course. Mainly just to pratice and since Mid-field has been my benchmark test track since when I started GT3 (before that, Clubman and Speical Stage Route 5 were my test tracks for cars ^^...including Laguna Seca and Grudenward...and God knows I miss high speed ring...), I woun't say how I did on that, from waht I can tell...you just need to learn how to be a little smoother with your drifts.
From what I can tell...yes, 300+ is a LOT for that car, I guess lowering the power would not hurt much, least till you get to maybe 200 or 240... although I have yet to really sample the SS, I would suggest pratcing with feinting a bit...try and learn weight control a little more so than usuall and try to get the car sliding a bit more so before the start of a turn, not so much but just maybe over 50 or 100 meters before a turn if possible, it's not always so, and with some of my cars (Grand Sport and Z28 to name 2) it seams easier to start drifting earlier...(my only expericne I recall with a Trueno besides the 245bhp Turbo (in red and only so to not be confused with the white Trueno my bro has and also the SS version...) I use is a bit with the SS...just haven't had a lot of time to pratice with it...) so you can decrease that angle on the exit...
My style with the bigger American cars is to feint to the outside before the inside, with ligher cars like the Trueno or S13 (2000k, 280bhp, no real suspesnion mods, just changes to engine and LSD, can drift that thing okay but I'll get to suspension soon enough...) I do something similar but not as drastic due to how I want to keep that speed and I can't regain as easily with more powerfull and heavier cars, just pratice and hell, try to experiment with other cars, we all start somewhere in some form.
For me, I started with the Z28 with 320bhp, with nearly everyting else modifed (but noting permenant) on Special Stage Route 5 WET to get used to the lack of traction (and I started on sims since it occured to me those would work best besides how they are supposedly simulating how a car behaves in RL, they aren't called sims for noting and plus they are closer to reality than one would think, the Z06 does oversteer like they talk about in Road and Track...trust me...heh...) before I got on dry, it was only when I got to get some solid WEEKS of pratice (solid because I had to study and crap, can't always be focued on games...school work counts too you know...)...okay a few days at the least before I started to drift well.
The only other suggestions I ask is to try and get as much angle as you can at the start and/or before the middle or apex of a turn and decrease thatn angle on the exit. I'm not sure how others would define a drift but that's how me and my bro look at it and also how some people at Initial D see it (I've noticed I repeated myself a bit...)
I noticed that Silva Drifter suggested to use both Analog sticks, I woun't argue, but for me, even though I use one stick for steering, I still use the buttons for acceleration and brake.
Now you may wonder just why but well... knowing that the PS2 buttons are pressure sensitive...I did my best to take advantage of that feature to try and learn critical and sensitive control, I think partial help came from using a steering wheel a few times, not just on GT3 but GT2 and Live For Speed, also, it was far from easy but for now, it's second nature to me and I've been drifting well, I still haven't elimated completely that slight 'jolt' when recovering from a drift, some of my drifts still show it but a lot of the time, I've learned how to smoothly recover from drifts, but this is just my case, I don't know about other people so I really can't say, I guess for now just to go with Silvia drifter's suggestions (he did give some good ones, since some of them I do use...although the gear ratios for some of my cars...Trueno included are short...I try not to bounce off the redline...) and other's whom I'm sure have been helpfull...
Well that's what I've got to say, sorry for not sounding more organized (or intelligent for the matter...) but...oh well... till later...
Go to manual now!!! I'm really serious bud. I should've figured that out from the vid. But start using a manual right now and you'll gain back that lost control. 
