You cannot believe the messes on autos this creates. All the dealers i've worked in have been burned mightly in these situations. Cars that have had convertiors removed,gas tank necks modified. Service engine soon lights unhooked and major emmision items butched etc. Used car sales for a long time never checked autos(trucks)out just drove them and then would not have them inspected after trade in etc. Resale the auto and folks come back with problems and emmisons warranty void etc. The dealer would eat any and all repairs. Even autos from the big sales. They finally got smart and started getting us in service to check them before accepting for trade and running them through service before resale. Sometimes they still get burnt. Over the years i've seen some real butched cars traded in. Air bag lights removed and the list goes on. Even had a tech not long ago trade in a late model DakotaV8 with headers,cam,mopar high rise. A EFI Dakota. At times it would stall for no reason,manual trans roared. The new owner showed up and said its all covered isn'nt it?He had a breakdown policy we had sold him. YEA RIGHT. The mech. adjuster that showed up to look at it said YEA RIGHT!Had to refund his money on policy and some one coughed up $2000 to fix the beast. It still stalled intermintaly at idle. We in service finally washed our hands of that truck. Told service manager what ever it took to please get that monkey off our back(service)Never really knew the total outcome of that deal.