My brother owns a stock 91 Tsi Awd and for a couple weeks now when he brings it past 3k it bogs out. It almost comes to a complete hault. When that happens he just shifts it up a gear and it doesnt do it untill hes over 3k. We changed the oil, fuel filter b-c we were thinking it was fuel cut but its a stock car. He doesnt want to take it down to the mitsubishi dealer b-c they are crooks like all other dealers. Can anyone give us any suggestions? Your help is greatly appreciated.THank you