I have the MBRP 4" turbo back kit. They have aluminumized, T409, and T304. Aluminumized is what came stock on our trucks. T409 stainless steel is the way better than aluminumized. T304 stainless Is a higher quality stainless steel than T409. The T304 usually has a pollish finish and will outlast the T409. I selected the T409 because the aluminumized lasted me 11years, and was still good upon removal. The T409 should outlast my truck. Also I payed $350-$450 (can't remember) compared to almost $800. Great sound and quicker spool up. Unknown the effects on EGTs. I had no baseline to go by. Good luck