I've seen several threads where people immediately suggested an air leak.
Yup. Look for the simple fixes first.

I don't want to open a can of worms here, but search on this site for glow plug options.
No can of worms here. Glow plugs are different as night and day. What a pilot usually ends up doing is picking one plug he likes and sticking with it on all his similar-type engines.

Now, HERE'S a can of worms - I'll recommend a plug! Personally, I like the McCoy 9 or 59 plugs. They're reliable and tough. The 59 is a hot plug, good for low nitro, low compression, rich idle, and cold weather conditions. The 9 is colder, and works well with 25% nitro and high compression engines, like the Webras.

Dr.1