On my Silver '87 Turbo I had a 62-1 CT26 with a full 3in/80mm exhaust w/3in turbo elbow. A hacked together homemade DDP picked up 22whp & 30wtq at 18psi, which brought me from 377whp to 399.2, and 428.8rwtq.
The rest of the setup was a VPC, SAFC, 550cc injs, MK4 TT pump, j-tube bypass, ZT2 wideband, upper IC hardpipes, AEM cam gears & an ACT street clutch. So, modwise I didn't have a lot of money in the car.
But in the process of actually learning the reality of keeping a 7M-GTE reliable at that power level cost me thousands and thousands more in proper maintenance/replacement parts, and lessons learned the hard way with blown motors.
Building a fast & semi-reliable 7M is quite a task, and I have to agree with Simba about the huge amount of 'knowledge' that is horribly mis-guided and overeager. I had to un-learn a great deal of things to get my MK3 to where it was.
As for the MK3 vs AT competition, I used to race my GF in the ST185 I bought for her in my red '89 turbo 5-spd targa MK3 daily I had at the time, and both cars being nearly 100% stock the 185 would edge me out about 1.5 cars to 50-55ish and I'd reel her back in around 70 and be ~2 cars past her at 100 or so. Both cars at stock boost.