You did read all the information right? With high-lift, your idle will increase to ~1000 RPM (it will idle below that, but sound like a musscle car).
The pistons will need to be notched with the high-lift/long duration to prevent collision.
Low end will suffer to get the high end. HP is related directly to RPM, so you get more RPM and therefore more HP with the increased redline, but you sacrifice the low end. This is why these radical cams are reccomended for race only, where the RPMs are high all the time.
I looked into all the performance options for the 1.9 before I decided to go with a swap. There IS a weight penalty for the bigger engine, (although the aluminum 2.8 from the Z3 is about the same) but the overall performance is greatly improved.
200 HP is about right for this car, and easily obtained with the DASC and a few other easy mods. If you don't have the blower, I suggest it. If you want more than 200 (reliable, streetable) HP, then the swap is where you should be looking.
This is not to say you can't get over 200 from the four, it is quite possible, but if it's a daily, year-round driver, the cons outweigh the pros on this one... | 
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