HELP! Problems with Shark Injector

[Russell328is]

Okay guys, I need some advice here. I've been very happy with the performance increase I've gained from the Shark Injector with my 1997 328is 5sp. The car just pulls stronger, and I've done a few back to back comparisons after un-sharking and re-sharking with good results.

However, in the last 6 months I've been finding that after running my car hard (whether that is lots of WOT around town or sustained high RPMs and WOT on the freeway) it begins to get very sluggish below 4k, especially noticeable in 1st gear. Idle becomes rough, power is decreased, and the car hesitates under light or no load (knock sensor?). Once or twice during one of these hesitations, the check engine light has flashed for an instant and then gone off. Also, it frequently stalls when coming to a stop with the clutch in.

I've changed spark plugs, flushed the fuel system, cleaned the injectors, and have always used 93 or 94 octane gas. My uneducated guess is that the JC software is somehow allowing the too much heat and compression (especially with 94 octane fuel) so that when I drive really hard, there is detonation and then the knock sensor steps in to compensate making my car feel like it's in "limp home" mode. Last night after a 5 hour highway drive, the car was exhibiting the behavior. As an experiment I unsharked the car, and sure enough it became very smooth again. I drove the car hard around town for a while to see if I could get the behavior to appear, but I couldn't. I've been driving with the car unsharked, so it's a little slow, but operates much better and more consistently under heavy load.

Does anyone have advice or experiences to share? Do I just need to keep re-sharking the car every few thousand miles, or is this $399 down the drain?