So I just picked up a mbrp 4" turbo back exhaust system for my early 99 PSD. The dp is also 4". Just wondering if I am in for any surprises? I don't know if the turbo exhaust side is smaller or if I need to beat in the firewall like an obs ford. I ordered the kit for a 99-03 there was not an early 99 kit. Just trying to get a heads up b4 I find out the hard way and have my truck down for days. Thanks.