You feel your connection internet is good ?? but when you download a something file using internet download manager, the speed or connection is bad ??? okey, i think there is a mistake in your IDM...maybe setting in IDM is not very good...And Now, you can use this software, is IDM Optimizer v.01 to improve your IDM Speed download....
How To Improve IDM Speed With IDM Optimizer
• You can download on the link above, and launch the aplication without install
• and then, click the button "optimizer IDM!" and try your speed connection download
• if not success, you can click the button "Default" to return first setting..
• Good Luck !!