In the summer, I would just put in a few percent of new veggie oil (1/2 to 1 gallon per tank full). In the winter I would mix 1 gallon of gasoline with 3 gallons of veggie oil and add that mix on each fillup.

The VO really smoothed out my idle.

A shot of cetane boost (Diesel Kleen? from WalMart?) wouldn't hurt either.

Fix your leaky lines. They probably were bad even before you went to ULSD.

__________________
Ron Schroeder
'85 300 Turbo Diesel 2 tank WVO
'83 300 Turbo Diesel 2 tank WVO
Some former WVO vehicles since ~1980:
'83 Mercedes 240D
'80 Audi 4000D
'83 ISUZU Pup
'70 SAAB 99 with Kubota diesel
'76 Honda Civic with Kubota diesel
'86 Golf
Several diesel generators
All with 2 tank WVO conversion
LI NY