01 Insight MT w/119K on it. Started bucking at low throttle. Was fine when cold but almost undrivable after about 10 minutes. Had thrown codes for cat (420) and running too rich (172). Independent shop first tried valve adjustment. Exhaust valve were too tight but made no difference in drivability. Next thought it was coil. I insisted it was most likely EGR based on this forum and other reports. Shop replaced EGR (non-OEM), also removed spacer plate between block and intake manifold and cleaned all the grooves. Made no difference. Tried different coils, no difference. Threw up hands and said take it to dealer. Dealer said it must be the EGR and the new one must have been bad. Replaced with OEM. No difference. Send a snapshot to HQ and the brain trust told them to clean out EGR port in engine block with special tool. $500 later, no difference. Next HQ wanted me to pull the head, thinking problem with #2 cylinder. Comp in cylinders is 170/140/160. Did a leakdown test and it was 5%/35%/12%. Consulted with several mechanics and they said pulling the head wouldn't do anything for the problem and low compression (140) and high leak (35%) in #2 wouldn't account for the problem. Now running with EGR unplugged and seems fine. Not throwing any codes. So, fellas....if it is the EGR system, but not the valve or the spacer or the port in the block, what does that leave?