Front Airbags not filling at idle??

I just went through a situation similar to this, except it was the whole system was airing up slow even at fast idle. It worked well and fine going down the road at higher rpm, but took forever to build initial air, raise chassis and rebuild air before leaving. I took a squirt bottle under the coach with it running and trying to build air, tires blocked and emergency off, and started looking for leaks. Accidentally bumped a line and got a shot of air out of it. Found the leak in the main line running from the compressor to the air dryer. It had chaffed a hole through it in a clamp that was holding it to prevent chaffing. Once fixed, Air builds up normal and ready to go. I would also check your airlines running from the air dryer to the front tank in the process of looking for a leak. Move the line around. To find a leak in the source line, you probably should have the engine running and compressor pumping also. Just what happened to me, Hope this may help, Happy trails Bert