I had an l series for over 2 years and had not 1 problem. Can be tuned to 150bhp/250ftlb for about £500 as well.
At the last OcUK RR day I took my old 400 diesel with the L series, it made 130bhp / 193ftlb and cost 50 quid to get it there from 103bhp standard. Score
Thinking it needs a new MAF as over 3000rpm it drops off power, but no biggie. First proper drive last night, and it's fantastic.
Cheers for the comments, I know it's basically a 400 diesel but damnit, it drives goooood.