Ok here is the thing... I tried to gather as much info as I could on this before I posted this, so all of you are welcomed to correct me or add you experience if it differs from mine. Also the fact that it has only been half a day since I Installed my new N75, [or solenoid (pt # 058 906 283 F) as they call it here in the dealership where I bought it] I will keep you guys updated if anything changes. Oh and another disclaimer... lol... and that is excuse my English please as English is my second language.
First of all before we go any further on this let me tell you that all this N75 adjustment is a voodoo science and it's really in the shade of gray. If you try to adjust your valve, you WILL break it, as it is not designed for adjustment. So you will have to dish out for the new one unless you have a friend that works for the stealership. The new valve cost me $98 tax included and will, give or take a little, cost you about the same. Also the only mods I am running now are Upsolute V5, K&N and Baily DV.
Well Ok here it is Yesterday I got tired of surging and I realized after some research that it is not by any means Upsolutes fault. It is in fact wastegate control settings fault that slightly differs from car to car. This slightly different setting from car to car is what causes some car to surge and some not. I also believe that this settings is what makes some motor a "freak" motor and runs a little stronger as it's wastegate settings are on the borderline of "normal"
I try adjusting the N75 as some here tried, following the tips from previous posts on vortex. Needless to say I messed up the valve settings thus cause my wastegate to perform out of factory specs, which in my case caused loss of power. In fact my car behaved like my old car (stock 2001 1.8T) That probably means that I was running about .5 bar boost, as I my dv was not as loud as it was before. Unfortunately I don't have the VAG-COM (jet...lol... as I see more and more need for this little tool) so I didn't log 002 block, and could not see if my car threw any trouble codes. What I understand unless you unplug it you won't see ant DTC's. Well I ordered the new one right away after I spoke to Slvrbllt (really cool and knowledgeable guy on this matter). It was in waiting for me the next day so I installed the new one and voila... surging solved.
This proves couple of things:
1) This surging on 2002 AWP is NOT Upsolutes fault. Which I would like to put as much emphasis because I don't want all these new guys with 2002 Jettas and GTI's to rule out Upsolute because they have read some disinformation on vortex.
2)Wastegate settings slightly differ in side of factory parameters which is not that critical on the stock car but as we chip our cars we can push those factory wastegate settings right over the edge so ECU starts to compensate for that (in my case ECU was quickly opening and closing the wastegate to control the overboost so I had this off and on surging from 3000-4000 rpm's that felt like rocking in my car)
3) Do not mess with N75 if you don't want/can't afford, to replace it with the new part because as soon as you turn that screw the settings inside change so you cannot (unless you are really lucky) put it where it was even if you mark the original position.
4) Solution to surging, that many of you are experiencing with 2002 AWP's, is replacing N75 with the new one but there is no guarantee that the new valve will not make you surge again because they are pre-set in the factory and they vary in between those factory parameters.
Good luck guys with this. Let me know how it went if for you and sorry about the novel length of this post but I felt a need to clear this up.