I know this topic has been beaten to death but I'm trying to get the most out of my 2hp HF DC. I added about 15 feet worth of 4 in. PVC and the suction was great to all tools. My plan was to add a cannister filter and chip separator. I added the Donaldson P181038 Filter and immediately noticed a drop off in the suction. With one blast gate open I noticed the vortex action in the bag was quite less. Opening up another increases the action but obviously reduces the suction. From what I've read, the cannister filter should have improved the suction but that's not what happened. I can use it like this but this means I'll be clogging the filter very quickly. I also tried to add a separator with a 31 gallon garbage can while venting the exhaust outside and just bypassing the filter. Same result! Actually, the suction was even worse using the separator. I've read tons of posts on the web claiming success with these mods but it seems this unit may not be up to the task. If anyone has any tips or suggestions, I'd love to hear them. It's good enough with just the donaldson filter but I was hoping for better results.