Any word on if this fixed your problem HeavyR?
Have the boost/running under full load difficulties with these cars above been resolved to a proper and satisfactory degree??? These are TWO distinctly different variations of the same system...early and late....The problems as described, usually, have little to do with "tune-up" and maintenance issues, but are problems focal to the safety circuitry of the boost circuitry... I have some pretty extensive experience with all variants-stock, modded, and comp variants.... What is essential, is full and total disclosure of EXACT model, date of manufacture, ORIGINAL stock configuration, current configuration-ESPECIALLY IF DIFFERENT THAN BASELINE-and original intended delivery market. All this info is critical to begin the journey... PM me if you prefer a more confidential discussion, at your leisure...
UPDATE-after reviewing my notes, i"m going to venture that the problem is going to be in a very discrete area of focus: the RATE of the turbos spooling up....this is solely tied to back pressure changes made from baseline stock. The timing equation in the 32-pin eprom chips which control EVERYTHING, is a partial differential equation in more than 5 variables-if memory serves correctly....ANY tipping of the variables will crash the location of the calc for the mapping values point(3d).... IF this car came with cats OEM-then it has a multi membrane, duty cycled, 5-volt control closed circuit... .REMEMBER: this system has not 1, not 2, not 3, but MANY "primary load sensors" with which said equation has command/control with....It is NOT a single order constant coefficients differential equation.... It SOUNDS as though ALL of your SENSORS and ACTUATORS have been proofed/functionality verified... That said: ONLY command and control is different-WHY? SOMETHING has been changed from baseline, without understanding the impact-however minor-this might make to the control side of the ECU....