I have a 2006 987 Boxster S Tiptronic with 28,000 flawless miles until 2 weeks ago. The air oil separator failed and the car was towed to my long time and trusted independent MB and Porsche mechanic. At a previous oil change he had mentioned that my transmission pan gasket was showing a small leak and I should consider a transmission service soon, but no rush. Since he had the car for the AOS repair, I had him do the transmission service at the same time. The repairs were completed, codes were cleared and no pending codes showed. Prior to these repairs I had no problems at all with the Tiptronic in either Auto or Manual modes. After these repairs the Tiptronic in Auto shifts up and down properly as before. HOWEVER, in Manual mode down shifts are smooth and quick, BUT upshifts above 4000 RPM now have a pronounced lag and a strong thump into gear. I found the lag and thump could be avoided if I briefly lifted the throttle before the upshift. Previous to the repairs above, I could start in 1st, take it up to 6000 RPM, shift and so on in every gear with smooth crisp shifts while mashing the throttle to the floor. So, I took the car back had my mechanic and had him test drive it and check for codes...he said the trans was behaving normally, no faults detected and that I should lift up on the throttle momentarily before each shift under heavy acceleration to "reduce the load" on the engine. Never had this problem before...why now? I'm not happy with his explanation. What possibly went wrong during the AOS repair and Trans service to cause this? Sorry for the long winded and detailed history, but it may help narrow down the problem. Thanks in advance.