If you have your IP seal replaced and Vehicle still hard starts and runs rough initially, Inspect Glow plugs Rail . You probably have the old 1st Generation Aluminum Rail that attaches all the glow plus together. The attaching point is at the number 1 or 2 glow plug nut and the terminal is probably overheated and cooked! This causes High resistance and not all the current will be going to the glow plugs.
Also Upgrade to NGK Ceramic Plugs for awesome starts in Cold weather.

Fix: Replace with 100% copper 4TH Generation Rail.