Should have replace the Timing Chain Tensioner when you have "Marble in a Can" sound at start up. When you have a " Diesel" sound, it's too late and the Timing Chain Guide need to be replaced.
GL with your choice. I'd rather replace the Timing Chain Guide and enjoy the 4.6iS, even though the Cherokee SRT8 isn't a bad replacement.

giodog2000, you have N62 engine in your 4.8iS, not the M62TU in the 4.6iS. I haven't heard or see thread about its chain guide. You have the rear main seal to deal with though.

__________________

00 E39 DINAN S1 //M5 (82k miles)
06 E53 DINAN 4.8iS, born 2/18/2006 (126k miles) http://www.xoutpost.com/bmw-sav-foru...s-my-dslr.html
90 Straman Z32 TwinTurbo Convertible, (1 of 44 ever made) 5 speed, 444rwhp/451rwtq
01 360 Novitec Spider F1 (26k miles)