some of the cheaper ones put STUPID restrictions on what you can and cannot do with your motor. Must be installed by a pro, must use OEM blah blah blah, must change oil every 500 miles, if broken, must be repaired by a pro...stuff like that. much better to rebuild your own motor.
The guy i bought mine from said some bull crap about that too, i then walked over to my truck and pulled out my useless ase card, gave it to him and asked if he would like a photocopy. In hind sight i should have known better as he beat my usual engine vender by 800 bucks. I have seen more shotty workmanship from back techs then from customers/ shade-tree mechanics.
