FYI, the Toytec kit will have the same problems as any other lift setup at the same height, be it a spacer kit, springs, adjustable shocks, whatever.
I run 1.5" rear spacers, my brake lines are definitely stretched tighter than stock but they're alright. I think with any more lift they would get pulled on during rear articulation.
Less caster (which occurs as you raise the front with stock UCAs) will make your truck feel "squirrel-y" and require constant steering corrections. I ran a 2.5" Daystar spacer lift up front with stock UCAs, the lack of caster was definitely noticeable and manageable although unpleasant on less-than-perfect roads.
While it's not specific to Toytec, here is the exact wording on these issues from the Suspension FAQ sticky you've already read.
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As you get closer to 3" lift, you can begin to run into other issues. Three things come to mind.
First, at 3" and higher, you begin running out of caster adjustment on the stock upper control arms (UCA's). Aftermarket UCAs may be required to get the front end alignment back into spec.
Here's a great thread discussing various options and benefits of the different UCA's offered.
Second, it's fairly common for there to be contact between the swaybar and front coils. To resolve this, you need to install swaybar relocates. There's no definite way to know you'll need these. My suggestion is that if you're going for 3"+ of lift, you probably should go ahead and invest in the relocates.
A third thing is a diff drop, which is intended to reduce the angle on the CV's. It's the general opinion that these do very little to improve the angle and are not worth installing.
Info courtesy of Mark at OW
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Just as a notice of warning for many who install lift kits on 4th and 5th Gens...
Please be aware that when lifting your rig in the back you can stretch the rear brake line if you are not careful.
Check by raising your truck off the ground and allowing full droop. Check your brake line where it changes from hard line to rubber line (look for it roughly the left side of the rear axle as it comes down from the body).
Now you also need to confirm that your are at full flex! Get someone to stand on the left tire to make sure.
At Overland Warehouse we include a brakeline extension bracket with our extended travel kits to alleviate this problem. You can also change to longer braided lines but then, beyond the cost of the lines, you also have to drain and bleed the brake system.
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