Does jaIlbreaking your iPhone/ iPod make your device slow?

Does jaIlbreaking your iPhone/ iPod make your device slow?

I have an iPhone 3g and had it jailbroken over a year ago. I use Simple Mobile and internet surfing is a bit slow but for unlimited everything for $40/month… I'll deal with it LOL

No, but the things you install on it may make it slow. If you install anything that makes use of MobileSubstrate, you will notice a slowdown in your device. You will know what makes use of it, because it will be listed when you try to install certain things from Cydia, most notably tweaks.

I only jailbreak for Installous.