Audi TT revised

Ok, here we have an audi i started a fair while ago. I fixed up all the crap modelingon my behalf from a fair while ago. I added some optioned parts such as some skirts, exhaust, spoiler...... One major issue i have with the car is that, when i render it with a HDRI, the car reflects very weird. i get really hard spots of green and in some parts the car will go tranparent and show the parts on the inside of the car. I have tried makeing a new material, merging the scene into a new one, lots of stuff and yet no reslut. The only way is not to us a HDRI but then i have dodgy chrome. If anyone has any ideas, please can you help me out. After all that, what do you think of the car ? DP you like the colour ? I have experimented a fair bit with colours and decided on the "glossy undercoat". ALso how a bout the wheels ? I was unsure weather to use the rims from the yellow golf but i stuck with these. The car body work has a very weird imperfections, for example above the front wheel arch in the render from the back. There is like a black vent. Thats all very well and good but i did not put it there, according to the mesh it is filled and smooth and what not. But yet there is a "hole". This also has stumped me, just like with the HDRI issue.