993tt mystery engine events - advice appreciated

[foxj0001]

Hello,

I've recently acquired a 1996 993tt which is beautiful to look at and great fun to drive (I posted recent pix). All is well except for the following mysterious engine symptoms:

Event consists of the throttle pedal "going soft", accompanied by momentary loss of power and CEL transiently illuminates. All these simultaneous, the event is over in less than a second, CEL goes off, throttle response and power come right back. Happens when fully warmed up (or at least has not yet happened when cold). Happens up to 3 or 4 times within a 5min period. Happens whether driving hard, accelerating, or driving "family style". Even happened twice this morning at idle, as I was letting the engine cool down after driving to work. No backfire and seems like it is not misfiring, certainly not running rough. No smoke. Oil recently changed, has always had Mobil1. Using 93 octane pump gas, and I do not let the tank run too low before filling up.

Prior owner had ECU reprogrammed through Fabspeed, who also installed custom, "stock-like" mufflers (very quiet) which I had them take off and replace w muffler bypasses (not quiet!).

I had it to the dealer where I bought her to look into this and they told me that because she was chipped she was not storing any CEL-related codes, and they could not reproduce the symptoms.

So here I am, mystery unsolved. MAF sensor dirty? Distributor problem? ECU hiccup? Any ideas?

Thanks for thinking about it.

Jonathan