I can vouch for the lifter problems. My HCI swap was performed at 65,000 miles. At 71,000, I now have a lifter going out. I would have changed them out before, but I could not afford it. As for the valve springs, you cannot use stock ones. I have done more HCI swaps on 5.0 mustangs than I care to remember. The few people who, for whatever reason, ran stock valve springs, ALL had valve float problems. Yes, this all occured with the stage 1 TFS cam. As the stock springs allow valve float with the factory cam, any Ford tech or engineer will tell you that if you install ANY aftermarket cam, or 1.7 roller rockers, you need stiffer, aftermarket springs.